As filed with the Securities and Exchange Commission on July 3, 2003
                  Registration Statement No. 333-______________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
                           --------------------------
                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               CYTOGEN CORPORATION
         ---------------------------------------------------------------
             (Exact Name of Registrant as Specified in Its Charter)

           Delaware                                             22-2322400
--------------------------------                         -----------------------
 (State or Other Jurisdiction                                (I.R.S. Employer
of Incorporation or Organization)                         Identification Number)

                        650 College Road East, 3rd Floor
                           Princeton, New Jersey 08540
                                 (609) 750-8200
  -----------------------------------------------------------------------------
          (Address, Including Zip Code, and Telephone Number, Including
             Area Code, of Registrant's Principal Executive Offices)

                            Donald L. Novajosky, Esq.
                            Director, Legal Services
                               Cytogen Corporation
                        650 College Road East, 3rd Floor
                           Princeton, New Jersey 08540
                                 (609) 750-8222
             -------------------------------------------------------
            (Name, Address, Including Zip Code, and Telephone Number,
                   Including Area Code, of Agent for Service)

                          ----------------------------
                                    Copy to:

                           Richard S. Mattessich, Esq.
                                Hale and Dorr LLP
                        650 College Road East, 4th Floor
                           Princeton, New Jersey 08540
                                 (609) 750-7600

                          ----------------------------

  Approximate  date of  commencement  of  proposed  sale to  public:  As soon as
  practicable after this Registration Statement becomes effective.

      If the only  securities  being  registered  on this Form are being offered
  pursuant  to  dividend  or  interest  reinvestment  plans,  please  check  the
  following box. [ ]

      If any of the securities  being  registered on this Form are to be offered
  on a delayed or continuous basis pursuant to Rule 415 under the Securities Act
  of 1933,  other than  securities  offered only in connection  with dividend or
  interest reinvestment plans, check the following box. [X]

      If this Form is filed to register  additional  securities  for an offering
  pursuant to Rule 462(b) under the Securities  Act,  please check the following
  box and list the Securities Act  registration  statement number of the earlier
  effective registration statement for the same offering. _______.

      If this Form is a  post-effective  amendment filed pursuant to Rule 462(c)
  under the Securities  Act, check the following box and list the Securities Act
  registration  statement number of the earlier effective registration statement
  for the same offering. __________.

      If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]


                        --------------------------------





                                             CALCULATION OF REGISTRATION FEE


-----------------------------------------------------------------------------------------------------------------------
                                                                        Proposed         Proposed
                                                                         Maximum         Maximum
                                                          Amount        Aggregate       Aggregate         Amount Of
                                                          To Be           Price          Offering       Registration
          Title Of Shares To Be Registered              Registered     Per Unit(1)       Price(1)            Fee
-----------------------------------------------------------------------------------------------------------------------
                                                                                               

Common stock,
   $.01 par value per share...................          1,368,422         $7.43        $10,167,375         $822.54
----------------------------------------------------- --------------- -------------- ----------------- ----------------


(1)      Estimated  solely for  purposes of  calculating  the  registration  fee
         pursuant to Rule 457(c) under the  Securities  Act of 1933, as amended,
         and based  upon the  average  of the high and low  prices on the Nasdaq
         National Market on June 26, 2003.


                     --------------------------------------

The Company hereby amends this  registration  statement on such date or dates as
may be  necessary  to delay its  effective  date until the Company  shall file a
further amendment which  specifically  states that this  registration  statement
shall  thereafter  become  effective  in  accordance  with  Section  8(a) of the
Securities  Act of  1933  or  until  the  registration  statement  shall  become
effective on such date as the Commission,  acting pursuant to said Section 8(a),
shall determine.




The  information  in this  prospectus  is not complete  and may be changed.  The
selling  stockholders  named in this  prospectus  may not sell these  securities
until  the  registration  statement  filed  with  the  Securities  and  Exchange
Commission  is  effective.  This  prospectus  is  not an  offer  to  sell  these
securities and the selling  stockholders are not soliciting  offers to buy these
securities in any jurisdiction where the offer or sale is not permitted.

                   Subject to completion, dated July 3, 2003

PROSPECTUS

                               CYTOGEN CORPORATION

                        1,368,422 Shares of common stock


         This prospectus  relates to resales of shares of up to 1,368,422 shares
of our  common  stock,  $0.01 par  value per  share,  by  certain  institutional
investors  set  forth in this  prospectus  under  the  section  titled  "Selling
Stockholders".  Of the 1,368,422 shares of common stock,  1,052,632 have already
been issued to the  institutional  investors and 315,790  shares are issuable to
such investors upon the exercise of warrants with an exercise price of $6.91 per
share.  The  shares  of  common  stock  and  the  warrants  were  issued  to the
institutional  investors pursuant to a Securities  Purchase Agreement dated June
6, 2003.

         We will not receive any proceeds from the sale of the shares hereunder.

         The  selling  stockholders  identified  in this  prospectus,  or  their
pledgees,  assignees and successors-in-interest,  may offer the shares from time
to time through public or private  transactions at prevailing  market prices, at
prices related to prevailing market prices or at privately negotiated prices.

         On October 25, 2002, we received  approval from our  stockholders  at a
duly called and held special  meeting of  stockholders to effect a reverse split
of our common stock.  Our Board of Directors  thereafter  approved a one-for-ten
reverse split of our outstanding,  issued and authorized shares of common stock,
which  became  effective  on October  25,  2002.  All  numbers set forth in this
Registration  Statement  on Form S-3  reflect  the  effect  of such  one-for-ten
reverse stock split.

         Our common  stock is traded on the  Nasdaq  National  Market  under the
symbol  "CYTO." On June 25, 2003,  the closing sale price of our common stock on
Nasdaq was $7.09 per share.  You are urged to obtain current  market  quotations
for our common stock.


                            -----------------------

         Investing in our common stock involves a high degree of risk. See "Risk
Factors" commencing on page 4.

                            -----------------------

         Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus  is truthful or  complete.  Any  representation  to the contrary is a
criminal offense.

                 The date of this prospectus is [  ], 2003.




                                              TABLE OF CONTENTS

-----------------------------------------------------------------------------------------------------
                                                                                                
Prospectus Summary...............................................................................   2
Cytogen Corporation..............................................................................   2
The Offering.....................................................................................   2
Recent Developments..............................................................................   3
Risk Factors.....................................................................................   4
      We Have A History Of Operating Losses And An Accumulated Deficit And
       Expect To Incur Losses In The Future......................................................   4
      We Are Heavily Dependent On Market Acceptance Of ProstaScint and
       Quadramet For Near-Term Revenues..........................................................   4
      The Reduced Workforce At AxCell May Not Be Able To Implement AxCell's
       Business Plan.............................................................................   5
      We May Need To Raise Additional Capital, Which May Not Be Available........................   6
      Our Products, Generally, Are In The Early Stages Of Development And
       Commercialization And We May Never Achieve The Revenue Goals Set Forth
       In Our Business Plan......................................................................   6
      Our PSMA Product Development Program Is Novel And, Consequently,
       Inherently Risky..........................................................................   7
      All of Our Potential Oncology Products Will Be Subject To The Risks Of Failure
       Inherent In The Development Of Diagnostic Or Therapeutic Products Based On
       New Technologies..........................................................................   8
      Competition In Our Field Is Intense And Likely To Increase.................................   8
      We Rely Heavily On Our Collaborative Partners..............................................   9
      Our Business Could Be Harmed If Our Collaborative Arrangements Expire Or
       Are Terminated Early......................................................................  10
      The Termination Of One Or More License Agreements That Are Important In The
       Manufacture Of Our Current Products And New Product Research And
       Development Activities Would Harm Our Business............................................  10
      We Have Limited Sales, Marketing And Distribution Capabilities For Our Products............  10
      There Are Risks Associated With The Manufacture And Supply Of Our Products.................  11
      Failure Of Consumers To Obtain Adequate Reimbursement From Third-Party
       Payors Could Limit Market Acceptance And Affect Pricing Of Our Products...................  11
      If We Are Unable To Comply With Applicable Governmental Regulation We
       May Not Be Able To Continue Our Operations................................................  12
      We Could Be Negatively Impacted By Future Interpretation Or Implementation
        Of Federal And State Fraud And Abuse Laws, Including Anti-Kickback Laws,
        The Federal Stark Law And Other Federal And State Anti-referral Laws.....................  13
      We Depend On Attracting And Retaining Key Personnel........................................  14
      Our Business Exposes Us To Potential Liability Claims That May Exceed Our
       Financial Resources, Including Our Insurance Coverage, And May Lead To The
       Curtailment Or Termination Of Our Operations..............................................  14
      Our Business Involves Environmental Risks That May Result In Liability.....................  15
      Our Intellectual Property Is Difficult To Protect..........................................  15
-----------------------------------------------------------------------------------------------------

                                                       -i-

                                             TABLE OF CONTENTS


-----------------------------------------------------------------------------------------------------

      We Cannot Be Certain That Our Security Measures Protect Our Unpatented
       Proprietary Technology....................................................................  16
      We Are Currently Subject To Patent Litigation..............................................  16
      Our Stock Price Has Been And May Continue To Be Volatile, And Your
       Investment In Our Stock Could Decline In Value Or Fluctuate Significantly.................  16
      We Have Adopted Various Anti-Takeover Provisions Which May Affect The
       Market Price Of Our Common Stock..........................................................  17
      The Liquidity Of Our Common Stock Could Be Adversely Affected If We Are
       Delisted From The Nasdaq National Market..................................................  18
      A Large Number Of Our Shares Are Eligible For Future Sale Which May
       Adversely Impact The Market Price Of Our Common Stock.....................................  19
      Because We Do Not Intend to Pay Any Cash Dividends On Our Shares of
       Common Stock, Our Stockholders Will Not Be Able to  Receive a Return on
       Their Shares Unless They Sell Them........................................................  20
Special Note Regarding Forward-Looking Statements................................................  20
Use of Proceeds..................................................................................  21
Selling Stockholders.............................................................................  22
Plan of Distribution.............................................................................  23
Legal Matters....................................................................................  24
Where You Can Find More Information..............................................................  24
Information Incorporated By Reference............................................................  24
-----------------------------------------------------------------------------------------------------



         We have not authorized anyone to provide you with information different
from that contained or incorporated by reference in this prospectus. The selling
stockholders  are  offering to sell,  and seeking  offers to buy,  shares of our
common stock only in  jurisdictions  where offers and sales are  permitted.  The
information contained in this prospectus is accurate only as of the date of this
prospectus, regardless of the time of delivery of this prospectus or of any sale
of common stock.




                                      -ii-


                               PROSPECTUS SUMMARY

This summary highlights  important features of this offering and the information
included or incorporated by reference in this prospectus.  This summary does not
contain all of the information  that you should consider before investing in our
common stock. You should read the entire  prospectus  carefully,  especially the
risks of investing in our common stock discussed under "Risk Factors."

                               CYTOGEN CORPORATION

         Cytogen    Corporation    is   a    product-driven,    oncology-focused
biopharmaceutical  company  with an  established  and  growing  product  line in
prostate cancer and other areas of oncology.  Our FDA-approved  products include
ProstaScint(R)  (a  monoclonal  antibody-based  imaging  agent used to image the
extent  and  spread of  prostate  cancer);  Quadramet(R)  (a  therapeutic  agent
marketed  for the relief of bone pain in prostate and other types of cancer) and
NMP22  BladderChek(TM)  (a  point-of-care,  in vitro diagnostic test for bladder
cancer).  Our pipeline  comprises  of product  candidates  at various  stages of
clinical  development,  including fully human  monoclonal  antibodies and cancer
vaccines based on PSMA prostate  specific membrane antigen  technology,  or PSMA
technologies, which we exclusively licensed from Memorial Sloan-Kettering Cancer
Center.  We also conduct research in cellular  signaling through our subsidiary,
AxCell Biosciences.

         In addition to the products listed above, in August,  2000, we expanded
our product pipeline by entering into marketing,  license and supply  agreements
with  Advanced  Magnetics,  Inc. for  Combidex(R),  which is an  investigational
magnetic   resonance   imaging  (MRI)   contrast   agent  that  assists  in  the
differentiation of metastatic from non-metastatic lymph nodes. We hold exclusive
United States marketing rights to Combidex. Advanced Magnetics is continuing its
discussions with the FDA relating to outstanding  issues regarding an approvable
letter  received from the FDA in June,  2000, in an effort to bring  Combidex to
market.

         We  are  a  Delaware  corporation.   We  were  incorporated  and  began
operations in 1980 under the name Hybridex, Inc. and changed our name to Cytogen
Corporation in April 1980. Our executive offices are located at 650 College Road
East,  3rd Floor,  Princeton,  New Jersey 08540,  our telephone  number is (609)
750-8200 and our Internet address is  http://www.cytogen.com  The information on
our Internet website is not incorporated by reference in this prospectus. Unless
the context otherwise requires  references in this prospectus to "Cytogen",  the
"Company,"  "we,"  "us,"  and  "our"  refer  to  Cytogen   Corporation  and  our
subsidiaries.

         ProstaScint(R) and OncoScint(R) are registered United States trademarks
of Cytogen  Corporation.  All other  trade  names,  trademarks  or  servicemarks
appearing in this  Registration  Statement on Form S-3 are the property of their
respective  owners,  and not the property of Cytogen  Corporation  or any of our
subsidiaries. Quadramet(R) is a trademark of The Dow Chemical Company used under
license by Cytogen.

                                  THE OFFERING


                                                 
Common Stock offered by selling
stockholders...................................     1,368,422 shares

Use of proceeds................................     Cytogen will not receive any proceeds from
                                                    the sale of shares in this offering

Nasdaq National Market symbol..................     CYTO



                                      -2-


                               RECENT DEVELOPMENTS

         On  June 6, 2003,  we sold to the selling  stockholders  listed in this
prospectus,  1,052,632  shares of our common  stock and  warrants to purchase an
additional  315,790  shares of our common stock for aggregate  gross proceeds of
$5.0 million before transaction costs.

         On  June 10, 2003, our  stockholders  approved an amendment to our 1995
Stock Option Plan to increase the maximum  aggregate  number of shares of Common
Stock  available for issuance  thereunder from 450,263 to 650,263 and to reserve
an additional 200,000 shares of our Common Stock for issuance in connection with
such increase.

         On  June 16, 2003, we announced  that we entered into an agreement with
Berlex Labratories,  a U.S. affiliate of Schering AG, Germany, whereby marketing
rights  held by Berlex to  market  Quadramet  (Samarium  Sm 153  Lexidronam),  a
skeletal targeting therapeutic  radiapharmaceutical  for the relief of bone pain
in prostate and other types of cancer, in North America and South America are to
be returned  to us in exchange  for an upfront  payment and  royalties  based on
future sales. The transaction,  which is targeted for completion  within 90 days
of  entering  the  agreement,  and is subject  to our  obtaining  any  necessary
financing for the reacquisition.




                                      -3-



                                  RISK FACTORS

         Investing  in our  common  stock  involves a high  degree of risk.  You
should  carefully  consider the risks and  uncertainties  described below before
purchasing our common stock. The risks and uncertainties described below are not
the only ones facing our company.  Additional risks and  uncertainties  may also
impair our business  operations.  If any of the following  risks actually occur,
our business,  financial condition or results of operations would likely suffer.
In that case, the trading price of our common stock could fall, and you may lose
all or part of the money you paid to buy our common stock.

We Have a History of Operating  Losses and an Accumulated  Deficit and Expect To
Incur Losses in the Future.

We have a history of operating losses since our inception.  We had a net loss of
$2.0  million  for the three  months  ended March 31, 2003 and had a net loss of
$15.7 million for the year ended December 31, 2002.  Beginning in December 2001,
we began to equally share the costs of the PSMA  Development  Company LLC and we
expect to incur significant and increasing costs in the future to fund our share
of the joint  venture.  We had a net loss of $12.1  million  for the year  ended
December  31,  2001.  We had a net loss of  $27.3  million  for the  year  ended
December  31,  2000 which  included  non-cash  charges of $13.1  million for the
acquisition  of product  candidate  rights and $4.3  million for the  cumulative
effect of an accounting change following the adoption of Securities and Exchange
Commission Staff Accounting  Bulletin No. 101. We had an accumulated  deficit of
$358.3 million as of March 31, 2003.

In order  to  develop  and  commercialize  our  technologies,  particularly  our
prostate specific membrane antigen, or PSMA, technology, and expand our oncology
products, we expect to incur significant increases in our expenses over the next
several  years.  As a result,  we will need to generate  significant  additional
revenue to become profitable.

Our ability to generate and sustain  significant  additional revenues or achieve
profitability  will  depend  upon  the  factors  discussed   elsewhere  in  this
"Additional Factors That May Affect Future Results" Section, as well as numerous
other factors outside of our control, including:

     -    development  of  competing  products  that are more  effective or less
          costly than ours;

     -    our  ability  to  develop  and  commercialize  our  own  products  and
          technologies; and

     -    our ability to achieve  increased sales for our existing  products and
          sales for any new products.

As a result, we may never be able to generate or sustain significant  additional
revenue or achieve profitability.

We Are Heavily  Dependent On Market  Acceptance Of ProstaScint and Quadramet For
Near-Term Revenues.

We expect  ProstaScint and Quadramet to account for a significant  percentage of
our product-related revenues in the near future. For the year ended December 31,
2002, revenues from ProstaScint and Quadramet accounted for approximately 78% of
our product  related  revenues  and in the  three-months  ended March 31,  2003,
revenues from ProtaScint and Quadramet  accounted for  approximately  89% of our
product related revenues. In 2002, our product-related  revenue included revenue
from  BrachySeed,  which  accounted for 20% of our product related  revenue.  In
January  2003,  we served  notice of  termination  for each of our  License  and
Distribution  Agreement  and Product  Manufacturing  and Supply  Agreement  with
Draximage  with  respect  to both the  BrachySeed  I-125 and  BrachySeed  Pd-103
products.  As a result,  effective January 24, 2003, we no longer accept or fill
new  orders for the  BrachySeed  products.  In April  2003,  we entered  into an
agreement with Draximage formally terminating each of these agreements.


                                      -4-


Because our marketed  products  contribute  the majority of our  product-related
revenues, our business,  financial condition and results of operations depend on
their  acceptance as safe,  effective and  cost-efficient  alternatives to other
available   treatment  and  diagnostic   protocols  by  the  medical  community,
including:

     -    health care providers, such as hospitals and physicians; and

     -    third-party payors,  including Medicare,  Medicaid,  private insurance
          carriers and health maintenance organizations.

Our  customers,   including  technologists  and  physicians,  must  successfully
complete our Partners in  Excellence  Program,  or PIE  Program,  a  proprietary
training program designed to promote the correct  acquisition and interpretation
of  ProstaScint  images.  This  product is  technique  dependent  and requires a
learning  commitment on the part of users.  We cannot assure you that additional
technologists  and physicians will make this commitment or otherwise accept this
product as part of their treatment practices.

Currently,  Berlex  Laboratories,  Inc.  markets  Quadramet in the United States
through an  agreement  with us entered into in October  1998.  On June 16, 2003,
however,  we entered into an agreement with Berlex whereby marketing rights held
by Berlex to market  Quadramet  in North  America  and South  Ameirca  are to be
returned to us in exchange for an up front payment and royalties based on future
sales. The  reacquisition of the marketing rights to Quadramet is anticipated to
close within 90 days from June 16, 2003,  subject to our obtaining the necessary
financing for the upfront  payment to Berlex for such  reacquisition.  We cannot
assure you that we will be able to obtain the  necessary  financing to reacquire
the marketing rights to Quadramet from Berlex.  If we do reacquire the marketing
rights  to  Quadramet,  we  cannot  assure  you  that  that  we  will be able to
successfully  market  Quadramet  or that the  agreement  will  result in further
revenue for us in the future.  Currently,  we intend to market Quadramet only in
the United States. Sales of Quadramet outside of the United States would require
certain  regulatory  approvals  and  arrangements  with  third  party  marketing
partners and we cannot assume that we would be able to obtain such  approvals or
enter into such arrangements in the future.

We cannot  assure you that  ProstaScint  or Quadramet  will  achieve  additional
market  acceptance on a timely basis,  or at all. If ProstaScint or Quadramet do
not achieve broader market acceptance, we may not be able to generate sufficient
revenue to become profitable.

The Reduced  Workforce At AxCell May Not Be Able To Implement  AxCell's Business
Plan.

In September 2002, we implemented the  restructuring  of our subsidiary,  AxCell
Biosciences  Corporation,  in an effort to reduce expenses and position  Cytogen
for stronger long-term growth in oncology.  As a result, we reduced our staff at
AxCell by  seventy-five  percent,  suspended  certain  projects  at  AxCell  and
implemented other cost-saving measures.

The technologies under development at AxCell are complex and remain commercially
unproven.  Even if we are able to develop and  commercialize  a product  through
AxCell, there are a limited number of pharmaceutical companies and biotechnology
companies that are potential customers for such technology or product.

Although we believe that we have  retained the AxCell  personnel  who are key to
achieving  AxCell's goals and implementing its strategies,  we cannot be certain
that such reduced workforce will be able to implement  AxCell's current business
plan.  The  further  loss of any of  AxCell's  personnel  could  have a material
adverse effect on AxCell's ability to achieve its goals.

                                      -5-


We May Need To Raise Additional Capital, Which May Not Be Available.

We have  incurred  negative  cash  flows from  operations  since  inception.  We
expended, and will need to continue to expend, substantial funds to complete our
planned product  development  efforts,  including our PSMA programs.  Our future
capital  requirements  and the  adequacy of our  available  funds depend on many
factors, including:

     -    successful commercialization of our products;

     -    acquisition of complementary products and technologies;

     -    magnitude, scope and results of our product development efforts;

     -    progress of preclinical studies and clinical trials;

     -    progress toward regulatory approval for our products;

     -    costs of filing,  prosecuting,  defending and enforcing  patent claims
          and other intellectual property rights;

     -    competing technological and market developments; and

     -    expansion  of  strategic   alliances  for  the  sale,   marketing  and
          distribution of our products.

We may raise additional capital through public or private equity offerings, debt
financings or additional  collaborations and licensing arrangements.  Additional
financing may not be available to us when needed,  or, if available,  we may not
be able to obtain  financing on terms favorable to our stockholders or us. If we
raise additional capital by issuing equity securities,  the issuance will result
in ownership dilution to our stockholders.  If we raise additional funds through
collaborations  and  licensing  arrangements,  we may be required to  relinquish
rights to certain of our technologies or product candidates or to grant licenses
on unfavorable  terms. If we relinquish  rights or grant licenses on unfavorable
terms,  we may not be able to develop  or market  products  in a manner  that is
profitable  to us. If adequate  funds are not  available,  we may not be able to
conduct  research  activities,  preclinical  studies,  clinical  trials or other
activities  relating to the  successful  commercialization  of our products on a
timely  basis,   if  at  all,  with  the  result  that  our  business  could  be
significantly and adversely affected.

Our  Products,   Generally,   Are  In  The  Early  Stages  Of  Development   And
Commercialization  And We May Never  Achieve The Revenue  Goals Set Forth In Our
Business Plan.

We began operations in 1980 and have been engaged primarily in research directed
toward the development,  commercialization  and marketing of products to improve
diagnosis  and  treatment  of cancer and other  diseases.  In October  1996,  we
introduced for commercial use our  ProstaScint  imaging agent. In March 1997, we
introduced  for commercial use our Quadramet  therapeutic  product.  In 2001, we
launched  the  iodine  version  of  BrachySeed.  In May 2002,  we  launched  the
palladium  version of  BrachySeed.  In November 2002, we began  promoting  NMP22
BladderChek to urologists in the United States. In January 2003, we discontinued
our marketing and sale of the BrachySeed products.

Our PSMA  technologies  are still in the early  stages of  development.  We have
significantly reduced operations at our AxCell subsidiary,  which is responsible
for the development certain of our technologies.  We may be unable to develop or
commercialize these products and technologies.

                                      -6-


Our business is therefore subject to the risks inherent in the development of an
early stage biopharmaceutical business enterprise, such as the need:

     -    to obtain sufficient capital to support the expenses of developing our
          technology and commercializing our products;

     -    to ensure that our products are safe and effective;

     -    to obtain regulatory approval for the use and sale of our products;

     -    to  manufacture  our  products  in  sufficient  quantities  and  at  a
          reasonable cost;

     -    to develop a sufficient market for our products; and

     -    to attract  and retain  qualified  management,  sales,  technical  and
          scientific staff.

The problems  frequently  encountered  using new technologies and operating in a
competitive  environment  also may affect our  business.  If we fail to properly
address these risks and attain our business  objectives,  our business  could be
significantly and adversely affected.

Our PSMA  Product  Development  Program Is Novel And,  Consequently,  Inherently
Risky.

We are subject to the risks of failure  inherent in the  development  of product
candidates based on new technologies, including our PSMA technology. These risks
include the possibility that:

     -    the technologies we use will not be effective;

     -    our product candidates will be unsafe;

     -    our product  candidates will fail to receive the necessary  regulatory
          approvals;

     -    the product candidates will be hard to manufacture on a large scale or
          will be uneconomical to market; and

     -    we will not successfully overcome  technological  challenges presented
          by our potential new products.

Our other research and development  programs involve  similarly novel approaches
to human  therapeutics.  Consequently,  there is no precedent for the successful
commercialization  of therapeutic  products based on our PSMA  technologies.  We
cannot assure you that any products will be successfully developed from our PSMA
technology.  If we fail to develop such products for the reasons set forth above
or for any other  reason,  our business  could be  significantly  and  adversely
affected.

                                      -7-


All of Our Potential  Oncology  Products Will Be Subject To The Risks Of Failure
Inherent In The  Development Of Diagnostic Or Therapeutic  Products Based On New
Technologies.

Product  development  for cancer  treatment  involves a high degree of risk.  We
cannot assure you that the product  candidates we develop,  pursue or offer will
prove to be safe and effective, will receive the necessary regulatory approvals,
will not be precluded by proprietary  rights of third parties or will ultimately
achieve market  acceptance.  These product  candidates will require  substantial
additional investment,  laboratory development,  clinical testing and regulatory
approvals  prior to their  commercialization.  We cannot assure you that we will
not  experience   difficulties  that  could  delay  or  prevent  the  successful
development, introduction and marketing of new products.

Before we obtain  regulatory  approvals  for the  commercial  sale of any of our
products under development,  we must demonstrate through preclinical studies and
clinical  trials that the product is safe and efficacious for use in each target
indication.  The results from preclinical  studies and early clinical trials may
not be predictive of results that will be obtained in  large-scale  testing.  We
cannot  assure you that our  clinical  trials  will  demonstrate  the safety and
efficacy  of any  products or will result in  marketable  products.  A number of
companies in the biotechnology  industry have suffered  significant  setbacks in
advanced  clinical  trials,  even after  promising  results  in earlier  trials.
Clinical trials or marketing of any potential diagnostic or therapeutic products
may expose us to liability claims for the use of these diagnostic or therapeutic
products.  We may  not be  able  to  maintain  product  liability  insurance  or
sufficient  coverage may not be available at a reasonable cost. In addition,  as
we develop diagnostic or therapeutic products  internally,  we will have to make
significant  investments  in  diagnostic  or  therapeutic  product  development,
marketing,  sales  and  regulatory  compliance  resources.  We will also have to
establish or contract for the  manufacture  of products,  including  supplies of
drugs used in clinical trials,  under the current Good Manufacturing  Practices,
or cGMP,  of the FDA. We also  cannot  assure you that  product  issues will not
arise following successful clinical trials and FDA approval.

The rate of  completion  of clinical  trials also depends on the rate of patient
enrollment.  Patient enrollment  depends on many factors,  including the size of
the patient population, the nature of the protocol, the proximity of patients to
clinical  sites and the  eligibility  criteria for the study.  Delays in planned
patient enrollment may result in increased costs and delays,  which could have a
harmful effect on our ability to develop the products in our pipeline. If we are
unable to develop and  commercialize  products on a timely  basis or at all, our
business could be significantly and adversely affected.

Competition In Our Field Is Intense And Likely To Increase.

We face, and will continue to face, intense  competition from one or more of the
following entities:

     -    pharmaceutical companies;

     -    biotechnology companies;

     -    bioinformatics companies;

     -    diagnostic companies;

     -    academic and research institutions; and

     -    government agencies.

All of our products and product candidate are subject to significant competition
from organizations that are pursuing technologies and products that are the same
as or  similar  to our  technology  and  products.  Many  of  the  organizations
competing  with us have greater  capital  resources,  research  and  development
staffs and facilities and marketing capabilities.


                                      -8-


Before we recover  development  expenses for our products and technologies,  the
products  or  technologies  may  become  obsolete  as a result of  technological
developments  by others or us. Our products  could also be made  obsolete by new
technologies,  which are less expensive or more effective. We may not be able to
make the enhancements to our technology  necessary to compete  successfully with
newly  emerging  technologies  and  failure  to do so  could  significantly  and
adversely affect our business.

We Rely Heavily On Our Collaborative Partners.

Our success  depends in significant  part upon the success of our  collaborative
partners. We have entered into the following agreements for the sale, marketing,
distribution   and   manufacture  of  our  products,   product   candidates  and
technologies:

     -    license  from  The Dow  Chemical  Company  relating  to the  Quadramet
          technology;

     -    agreement  for  manufacture  of  Quadramet  by  Bristol  Myers  Squibb
          (formerly The DuPont Pharmaceuticals Company);

     -    joint venture with Progenics  Pharmaceuticals  for the  development of
          PSMA for in vivo immunotherapy for prostate and other cancers;

     -    licensing  agreement with Molecular  Staging for technology to be used
          in  developing  in vitro  diagnostic  tests  using  PSMA and  prostate
          specific antigen, or PSA;

     -    a Supply Agreement with Laureate Pharma L.P. for the production of our
          ProstaScint product;

     -    an agreement with Matritech to market and distribute NMP22 BladderChek
          to urologists and oncologists in the United States;

     -    marketing, license and supply agreements with Advanced Magnetics, Inc.
          related to Combidex and Code 7228;

     -    a License  Agreement  between  our  joint  venture,  PSMA  Development
          Company LLC, and AlphaVax Human Vaccines, Inc.;

     -    a Collaboration  Agreement between our joint venture and Abgenix, Inc;
          and

     -    sub-license  and marketing  agreement with Berlex  Laboratories,  Inc.
          relating to the  Quadramet  technology  which we licensed from The Dow
          Chemical  Company.  However,  on June 16,  2003,  we  entered  into an
          agreement  with Berlex to reacquire the marketing  rights to Quadramet
          in North America and South America. The reacquisition of the marketing
          rights to Quadramet is  anticipated  to close within 90 days from June
          16,  2003,  subject to us obtaining  the  necessary  financing  for an
          upfront payment to Berlex for such reacquisition.

Because our  collaborative  partners are  responsible  for certain of our sales,
marketing,  manufacturing  and  distribution  activities,  these  activities are
outside our direct control.  We cannot assure you that our partners will perform
their  obligations  under these agreements with us or that our partners will not
enter  into  arrangements  with third  parties  that may  negatively  impact the
economic  benefit we hope to derive from their  agreements with us. For example,
Matritech  retained the ability to market its NMP22  BladderChek to primary care
physicians  and others and has begun such marketing  efforts.  In the event that
our collaborative partners do not successfully market and sell our products, are

                                      -9-


entitled  to  enter  into  third  party   arrangements   that  may  economically
disadvantage us, or breach their obligations under our agreements,  our products
may not be commercially  successful,  any success may be delayed and new product
development  could be  inhibited  with the  result  that our  business  could be
significantly and adversely affected.

Our Business  Could Be Harmed If Our  Collaborative  Arrangements  Expire Or Are
Terminated Early.

We cannot assure you that we will be able to maintain our existing collaborative
arrangements.  If they expire or are terminated,  we cannot assure you that they
will be renewed or that new arrangements  will be available on acceptable terms,
if at all. In January 2003, we provided Draximage Inc. with notice of our intent
to  terminate  our  Product  Manufacturing  and  Supply  Agreement  and  License
Agreement with Draximage relating to the BrachySeed products.  In April 2003, we
entered into an agreement  with  Draximage  formally  terminating  each of these
agreements.

In  addition,  we cannot  assure you that any new  arrangements  or  renewals of
existing arrangements will be successful, that the parties to any new or renewed
agreements will perform adequately or that any former or potential collaborators
will not compete with us.

We cannot assure you that our existing or future collaborations will lead to the
development of product  candidates or technologies  with  commercial  potential,
that we will be able to obtain  proprietary  rights or licenses for  proprietary
rights for our product  candidates or technologies  developed in connection with
these  arrangements  or that we will be able to ensure  the  confidentiality  of
proprietary rights and information developed in such arrangements or prevent the
public disclosure thereof.

The  Termination  Of One Or More License  Agreements  That Are  Important In The
Manufacture  Of Our Current  Products And New Product  Research And  Development
Activities Would Harm Our Business.

We are a  party  to  license  agreements  under  which  we  have  rights  to use
technologies  owned by other companies in the manufacture of our products and in
our  proprietary  research,  development  and  testing  processes.  We  are  the
exclusive  licensee  of  certain  patents  and patent  applications  held by the
University of North Carolina at Chapel Hill covering part of the technology used
in the proteomics program and of certain patents and patent applications held by
the Memorial  Sloan-Kettering  Institute  covering PSMA. We also depend upon the
enforceability  of our license  with The Dow  Chemical  Company  with respect to
Quadramet. If the licenses were terminated,  we may not be able to find suitable
alternatives to this technology on a timely basis or on reasonable  terms, if at
all. The loss of the right to use these technologies that we have licensed would
significantly and adversely affect our business.

We Have Limited Sales, Marketing And Distribution Capabilities For Our Products.

We have  established an internal  sales force that is responsible  for marketing
and selling  ProstaScint  and NMP22  BladderChek.  However,  such internal sales
force  has  limited  sales,  marketing  and  distribution  capabilities  for our
products,  compared  to those of many of our  competitors.  We  depend on Berlex
Laboratories,  Inc. for the sale, marketing and distribution of Quadramet in the
United  States.  On June 16, 2003,  however,  we entered into an agreement  with
Berlex  whereby  marketing  rights held by Berlex to market  Quadramet  in North
America and South  America are to be returned to us in exchange  for an up front
payment and royalties based on future sales. The  reacquisition of the marketing
rights to Quadramet is  anticipated  to close within 90 days from June 16, 2003,
subject to our  obtaining the  necessary  financing  for the upfront  payment to
Berlex for such  reacquisition.  In locations  outside of the United States,  we
have not  established  a selling  presence.  If we are unable to  establish  and
maintain  significant  sales,   marketing  and  distribution   efforts,   either
internally  or through  arrangements  with third  parties,  our  business may be
significantly and adversely affected.

                                      -10-


There Are Risks Associated With The Manufacture And Supply Of Our Products.

If we are to be  successful,  our  products  will  have  to be  manufactured  by
contract  manufacturers in compliance with regulatory  requirements and at costs
acceptable  to us. We cannot  assure you that we will be able to arrange for the
manufacture of our products on commercially  reasonable  terms. If we are unable
to  successfully  arrange  for  the  manufacture  of our  products  and  product
candidates,  we will not be able to successfully  commercialize our products and
our business will be significantly and adversely affected.

ProstaScint was manufactured at a cGMP compliant manufacturing facility operated
by  Laureate  Pharma  L.P.  (formerly  Bard  BioPharma  L.P.).  We had access to
Laureate's  facility for  continued  manufacturing  of the product until January
2002.  We  entered  into a  Development  and  Manufacturing  Agreement  with DSM
Biologics  Company  B.V.  in July 2000,  which we  intended  would  replace  our
arrangement  with  Laureate with respect to  ProstaScint.  We entered into a new
Contract  Manufacturing  Agreement with Laureate Pharma L.P. in January 2003. We
have built our inventory of ProstaScint to meet our product  requirements in the
short term. Our failure to maintain a long term supply agreement on commercially
reasonable terms will have a material adverse effect on our business,  financial
condition and results of operations.

Quadramet is  manufactured  by  Bristol-Myers  Squibb (BMS)  (formerly  DuPont),
pursuant  to an  agreement  with both Berlex and  Cytogen.  Some  components  of
Quadramet,  particularly  Samarium153 and EDTMP,  are provided to BMS by outside
suppliers.  Due to radioactive  decay,  Samarium153 must be produced on a weekly
basis.   BMS  obtains  its  requirements  for  Samarium153  from  one  supplier.
Alternative  sources for these components may not be readily  available.  If BMS
cannot obtain sufficient quantities of the components on commercially reasonable
terms, or in a timely manner,  it would be unable to manufacture  Quadramet on a
timely and  cost-effective  basis, which could have a material adverse effect on
our business, financial condition and results of operations.

Pursuant to the terms of our distribution  agreement with Matritech,  we rely on
Matritech as the sole supplier of NMP22 BladderChek.  Matritech uses independent
contractors to manufacture  the product.  If Matritech fails to, or is unable to
provide  the  product,  we could  experience  a material  adverse  effect on our
business, financial condition and results of operations.

The Company, our contract manufacturers and testing laboratories are required to
adhere to United  States Food & Drug  Administration  regulations  setting forth
requirements for cGMP, and similar regulations in other countries, which include
extensive testing,  control and documentation  requirements.  Ongoing compliance
with cGMP,  labeling and other applicable  regulatory  requirements is monitored
through  periodic  inspections  and  market  surveillance  by state and  federal
agencies,  including  the FDA, and by  comparable  agencies in other  countries.
Failure of our  contract  vendors or us to comply  with  applicable  regulations
could result in sanctions  being imposed on us,  including  fines,  injunctions,
civil  penalties,  failure of the  government  to grant  premarket  clearance or
premarket  approval of drugs,  delays,  suspension  or  withdrawal of approvals,
seizures  or  recalls  of   products,   operating   restrictions   and  criminal
prosecutions any of which could significantly and adversely affect our business.

Failure Of Consumers To Obtain Adequate  Reimbursement  From Third-Party  Payors
Could Limit Market Acceptance And Affect Pricing Of Our Products.

Our business,  financial condition and results of operations will continue to be
affected by the efforts of governments and other  third-party  payors to contain
or reduce the costs of  healthcare.  There have been,  and we expect  that there
will  continue  to be, a number of  federal  and state  proposals  to  implement
government  control of pricing and  profitability  of therapeutic and diagnostic
imaging  agents such as our products.  In addition,  an emphasis on managed care
increases  possible  pressure  on  pricing  of these  products.  While we cannot
predict whether these  legislative or regulatory  proposals will be adopted,  or

                                      -11-


the effects  these  proposals or managed care efforts may have on our  business,
the  announcement  of these  proposals  and the  adoption of these  proposals or
efforts  could affect our stock price or our  business.  Further,  to the extent
these  proposals or efforts have an adverse  effect on other  companies that are
our prospective corporate partners, our ability to establish necessary strategic
alliances may be harmed.

Sales of our  products  depend in part on  reimbursement  to the  consumer  from
third-party payors,  including  Medicare,  Medicaid and private health insurance
plans.  Third-party  payors are increasingly  challenging the prices charged for
medical  products and  services.  We cannot assure you that our products will be
considered  cost-effective  and that reimbursement to consumers will continue to
be  available,  or will be  sufficient  to allow us to sell  our  products  on a
competitive  basis.  Approval of our products for reimbursement by a third-party
payor may depend on a number of factors,  including  the  payor's  determination
that our products are clinically useful and cost-effective,  medically necessary
and not  experimental or  investigational.  Reimbursement  is determined by each
payor individually and in specific cases. The reimbursement  process can be time
consuming.  If we  cannot  secure  adequate  third-party  reimbursement  for our
products, our business could be significantly and adversely affected.

If We Are Unable To Comply With Applicable Governmental Regulation We May Not Be
Able To Continue Our Operations.

Any products tested, manufactured or distributed by us or on our behalf pursuant
to FDA approvals are subject to pervasive and continuing  regulation by numerous
regulatory authorities, including primarily the FDA. We may be slow to adapt, or
we may never  adapt to changes  in  existing  requirements  or  adoption  of new
requirements  or policies.  Our failure to comply with  regulatory  requirements
could subject us to enforcement  action,  including product  seizures,  recalls,
withdrawal,   suspension,  or  revocation  of  approvals,   restrictions  on  or
injunctions  against  marketing our products based on our technology,  and civil
and  criminal  penalties.  We cannot  assure you that we will not be required to
incur  significant  costs to comply with laws and  regulations  in the future or
that  laws or  regulations  will  not  create  an  unsustainable  burden  on our
business.

Numerous federal, state and local governmental authorities, principally the FDA,
and similar  regulatory  agencies in other  countries,  regulate the preclinical
testing,  clinical trials,  manufacture and promotion of any compounds or agents
we or our collaborative partners develop, and the manufacturing and marketing of
any resulting drugs. The product  development and regulatory approval process is
lengthy, expensive, uncertain and subject to delays.

The regulatory risks we face also include the following:

     -    any compound or agent we or our  collaborative  partners  develop must
          receive regulatory agency approval before it may be marketed as a drug
          in a particular country;

     -    the  regulatory  process,   which  includes  preclinical  testing  and
          clinical  trials of each  compound or agent in order to establish  its
          safety and  efficacy,  varies from  country to country,  can take many
          years and requires the expenditure of substantial resources;

     -    in all  circumstances,  approval of the use of  previously  unapproved
          radioisotopes in certain of our products  requires  approval of either
          the Nuclear  Regulatory  Commission  or  equivalent  state  regulatory
          agencies.  A  radioisotope  is an  unstable  form of an element  which
          undergoes  radioactive decay,  thereby emitting radiation which may be
          used, for example,  to image or destroy harmful growths or tissue.  We
          cannot  assure you that such  approvals  will be  obtained on a timely
          basis, or at all;

     -    data obtained from preclinical and clinical activities are susceptible
          to  varying  interpretations  which  could  delay,  limit  or  prevent
          regulatory agency approval; and


                                      -12-


     -    delays  or  rejections  may  be  encountered  based  upon  changes  in
          regulatory  agency  policy  during the  period of product  development
          and/or the period of review of any application  for regulatory  agency
          approval.  These delays could  adversely  affect the  marketing of any
          products  we or our  collaborative  partners  develop,  impose  costly
          procedures upon our activities, diminish any competitive advantages we
          or our  collaborative  partners  may attain and  adversely  affect our
          ability to receive royalties.

We cannot  assure you that,  even after  this time and  expenditure,  regulatory
agency  approvals will be obtained for any compound or agent  developed by or in
collaboration  with us.  Moreover,  regulatory  agency approval for a product or
agent  may  entail  limitations  on the  indicated  uses  that  could  limit the
potential market for any such product. Furthermore, if and when such approval is
obtained, the marketing,  manufacture,  labeling, packaging, reporting, storage,
advertising  and  promotion  and record  keeping  related to our products  would
remain  subject to extensive  regulatory  requirements.  Discovery of previously
unknown  problems with a drug, its manufacture or its manufacturer may result in
restrictions on such drug, manufacture or manufacturer,  including withdrawal of
the drug from the market.  Failure to comply with regulatory  requirements could
result in fines,  injunctions,  seizures,  recalls,  suspension or withdrawal of
regulatory approvals, operating restrictions and criminal prosecution.

The United States Food, Drug and Cosmetics Act requires (i) that our products be
manufactured in FDA registered  facilities subject to inspection,  and (ii) that
we  comply  with  cGMP,  which  imposes  certain  procedural  and  documentation
requirements   upon  us  and  our   manufacturing   partners   with  respect  to
manufacturing and quality assurance  activities.  If we or our contract partners
do not  comply  with  cGMP we may be  subject  to  sanctions,  including  fines,
injunctions,  civil penalties, recalls or seizures of products, total or partial
suspension of production,  product  recalls,  failure of the government to grant
premarket  clearance or premarket  approval for drugs,  withdrawal  of marketing
approvals and criminal prosecution.

We Could Be Negatively  Impacted By Future  Interpretation  Or Implementation Of
Federal  And State  Fraud And Abuse  Laws,  Including  Anti-Kickback  Laws,  The
Federal Stark Law And Other Federal And State Anti-referral Laws.

We are subject to various federal and state laws pertaining to health care fraud
and  abuse,  including  anti-kickback  laws and  physician  self-referral  laws.
Violations  of these laws are  punishable  by criminal  and/or civil  sanctions,
including,  in some instances,  imprisonment and exclusion from participation in
federal  and state  health  care  programs,  including  Medicare,  Medicaid  and
Veterans  Administration  health  programs.  We have  not been  challenged  by a
governmental  authority  under any of these laws and believe that our operations
are in compliance with such laws. However, because of the far-reaching nature of
these laws,  we may be required to alter one or more of our  practices  to be in
compliance with these laws.  Health care fraud and abuse regulations are complex
and even minor,  inadvertent  irregularities can potentially give rise to claims
that the statute has been violated. Any violations of these laws could result in
a material  adverse effect on our business,  financial  condition and results of
operations.  If  there is a  change  in law,  regulation  or  administrative  or
judicial  interpretations,  we may have to change our business  practices or our
existing business practices could be challenged as unlawful,  which could have a
material  adverse  effect on our  business,  financial  condition and results of
operations.

We could become subject to false claims litigation under federal statutes, which
can lead to civil  money  penalties,  criminal  fines and  imprisonment,  and/or
exclusion from  participation in Medicare,  Medicaid and other federal and state
health care programs.  These false claims statutes include the False Claims Act,
which allows any person to bring suit alleging false or fraudulent  claims under
federal  programs or contracts  claims or other violations of the statute and to
share  in any  amounts  paid  by  the  entity  to the  government  in  fines  or
settlement.  Such suits, known as qui tam actions, have increased  significantly
in recent years and have increased the risk that a health care company will have
to defend a false  claim  action,  pay fines or be  excluded  from the  Medicare
program,  Medicaid programs or other federal and state health care programs as a


                                      -13-


result of an investigation arising out of such action. We cannot assure you that
we will not become  subject to such  litigation  or, if we are not successful in
defending  against  such  actions,  that such  actions  will not have a material
adverse effect on our business, financial condition and results of operations.

We Depend On Attracting And Retaining Key Personnel.

We are  highly  dependent  on  the  principal  members  of  our  management  and
scientific  staff.  The  loss of their  services  might  significantly  delay or
prevent the  achievement  of development  or strategic  objectives.  Our success
depends  on our  ability  to retain  key  employees  and to  attract  additional
qualified employees.  Competition for personnel is intense, and we cannot assure
you that we will be able to retain  existing  personnel  or  attract  and retain
additional highly qualified employees in the future.

During 2002, we announced  numerous changes to members of our senior management.
H. Joseph Reiser,  Ph.D. who held the position of President and Chief  Executive
Officer of the Company from April 1998 until  December  2002,  resigned from his
position for personal reasons.  Michael D. Becker,  our former Vice President of
Business Development, was unanimously elected by our board of directors to serve
as Dr. Reiser's replacement as President and Chief Executive Officer. Mr. Becker
was also unanimously elected to serve on our Board of Directors.  Dr. Reiser has
remained a member of our Board of Directors.  In addition,  Lawrence R. Hoffman,
our Vice President and Chief Financial Officer since July 2000, left the Company
to pursue  other  opportunities  as of  December  31,  2002.  Ms. Thu Dang,  our
Director of Finance, was subsequently promoted to Vice President of Finance.

Additionally,  in the first  quarter of 2003:  (i) William  Goeckeler,  our Vice
President  of  Research  and  Development,  was  promoted to Vice  President  of
Operations;  (ii) Deborah  Kaminsky,  our Vice President of Sales and Marketing,
shifted  her  work  focus,   and  serves  as  our  Vice  President  of  Business
Development;  (iii) Rita Auld, our Director of Human Resources,  was promoted to
Vice President of Human Resources and  Administration  and Corporate  Secretary;
(iv) Corey Jacklin assumed the responsibilities of Senior Director of Sales; and
(v) June Gobern was promoted to Senior Director of Marketing.

We do not typically enter into long-term arrangements with our key personnel. If
we are unable to hire and retain personnel in key positions,  our business could
be significantly  and adversely  affected unless  qualified  replacements can be
found.

Our  Business  Exposes  Us To  Potential  Liability  Claims  That May Exceed Our
Financial  Resources,  Including  Our  Insurance  Coverage,  And May Lead To The
Curtailment Or Termination Of Our Operations.

Our  business is subject to product  liability  risks  inherent in the  testing,
manufacturing  and marketing of our products.  We cannot assure you that product
liability  claims will not be  asserted  against  us, our  collaborators  or our
licensees. While we currently maintain product liability insurance in amounts we
believe are  adequate,  we cannot assure you that such coverage will be adequate
to protect us against future product  liability claims or that product liability
insurance  will be  available  to us in the  future on  commercially  reasonable
terms,  if at all.  Furthermore,  we cannot  assure  you that we will be able to
avoid significant  product liability claims and adverse publicity.  If liability
claims  against  us exceed  our  financial  resources  we may have to curtail or
terminate our operations. In addition, while we currently maintain directors and
officers  liability  insurance  in amounts we believe  are  adequate,  we cannot
assure you that such  coverage  will be adequate to cover any claims that we may
be required to satisfy in the future.


                                      -14-


Our Business Involves Environmental Risks That May Result In Liability.

We are subject to a variety of local,  state,  federal  and  foreign  government
regulations  relating to storage,  discharge,  handling,  emission,  generation,
manufacture and disposal of toxic, infectious or other hazardous substances used
to manufacture  our products.  If we fail to comply with these  regulations,  we
could be  liable  for  damages,  penalties  or other  forms of  censure  and our
business could be significantly and adversely affected.

Our Intellectual Property Is Difficult To Protect.

Our business and competitive positions are dependent upon our ability to protect
our  proprietary  technology.  Because  of the  substantial  length  of time and
expense  associated with  development of new products,  we, like the rest of the
biopharmaceutical  industry,  place  considerable  importance  on obtaining  and
maintaining  patent and trade secret protection for new  technologies,  products
and  processes.  We  have  filed  patent  applications  for our  technology  for
diagnostic and therapeutic products and the methods for its production and use.

The patent  positions of  pharmaceutical,  biopharmaceutical  and  biotechnology
companies,  including us, are generally  uncertain and involve complex legal and
factual questions.  Our patent applications may not protect our technologies and
products because, among other things:

     -    there is no guarantee that any of our pending patent applications will
          result in issued patents;

     -    we may  develop  additional  proprietary  technologies  that  are  not
          patentable;

     -    there is no guarantee that any patents issued to us, our collaborators
          or our  licensors  will  provide  a basis  for a  commercially  viable
          product;

     -    there  is  no  guarantee   that  any  patents  issued  to  us  or  our
          collaborators will provide us with any competitive advantage;

     -    there  is  no  guarantee   that  any  patents  issued  to  us  or  our
          collaborators  will not be challenged,  circumvented or invalidated by
          third parties; and

     -    there is no guarantee that any patents  previously issued to others or
          issued in the future will not have an adverse effect on our ability to
          do business.

In  addition,  patent  law in the  technology  fields  in  which we  operate  is
uncertain  and still  evolving,  and we cannot  assure  you as to the  degree of
protection  that will be  afforded  any  patents we are  issued or license  from
others.  Furthermore,  we cannot  assure you that others will not  independently
develop similar or alternative technologies,  duplicate any of our technologies,
or, if  patents  are  issued to us,  design  around  the  patented  technologies
developed by us. In addition,  we could incur substantial costs in litigation if
we are required to defend  ourselves  in patent suits by third  parties or if we
initiate  such suits.  We cannot  assure you that,  if  challenged  by others in
litigation, the patents we have been issued, or which have been assigned or have
been licensed from others will not be found  invalid.  We cannot assure you that
our  activities  would  not  infringe  patents  owned  by  others.  Defense  and
prosecution  of  patent  matters  can  be  expensive  and  time-consuming   and,
regardless  of  whether  the  outcome  is  favorable  to us,  can  result in the
diversion of substantial financial,  managerial and other resources.  An adverse
outcome could:

     -    subject us to significant liability to third parties;

     -    require us to cease any related  research and  development  activities
          and product sales; or

     -    require us to obtain licenses from third parties.


                                      -15-


We cannot  assure  you that any  licenses  required  under any such  third-party
patents or proprietary rights would be made available on commercially reasonable
terms, if at all.  Moreover,  the laws of certain  countries may not protect our
proprietary  rights to the same  extent  as the laws of the  United  States.  We
cannot predict whether us or our competitors'  pending patent  applications will
result in the issuance of valid  patents which may  significantly  and adversely
affect our business.

We  Cannot  Be  Certain  That  Our  Security  Measures  Protect  Our  Unpatented
Proprietary Technology.

We also rely upon  trade  secret  protection  for some of our  confidential  and
proprietary  information that is not subject matter for which patent  protection
is available. To help protect our rights, we require all employees, consultants,
advisors and collaborators to enter into confidentiality agreements that require
disclosure,  and in most cases, assignment to us, of their ideas,  developments,
discoveries  and  inventions,  and that prohibit the disclosure of  confidential
information to anyone outside Cytogen or our subsidiaries. We cannot assure you,
however,  that these agreements will provide  adequate  protection for our trade
secrets,  know-how or other proprietary  information or prevent any unauthorized
use or disclosure.

We Are Currently Subject To Patent Litigation.

On March 17,  2000,  we were  served with a  complaint  filed  against us in the
United  States  District  Court  for the  District  of New  Jersey  by M.  David
Goldenberg  ("Goldenberg") and Immunomedics,  Inc. (collectively  "Plaintiffs").
The  litigation   claims  that  our  Prostascint   product  infringes  a  patent
purportedly  owned by Goldenberg and licensed to  Immunomedics.  We believe that
ProstaScint  does not infringe  this patent,  and that the patent is invalid and
unenforceable.  The  patent  sought to be  enforced  in the  litigation  has now
expired;  as a result,  the claim,  even if  successful,  would not result in an
injunction  barring the continued sale of ProstaScint or affect any other of our
products or technology.  In addition,  we have certain rights to indemnification
against litigation and litigation  expenses from the inventor of technology used
in  ProstaScint,  which  may be  offset  against  royalty  payments  on sales of
ProstaScint.  However,  given the  uncertainty  associated with  litigation,  we
cannot give any  assurance  that the  litigation  could not result in a material
expenditure  to us. On December  17,  2001,  Cytogen  filed a motion for summary
judgment of non-infringement  of the asserted claims of the patent-in-suit.  The
Plaintiffs  opposed  that  motion and filed their own  cross-motion  for summary
judgment  of  infringement.  On July 3, 2002,  the Court  denied  both  parties'
summary  judgment  motions,  with leave to renew those motions after  presenting
expert  testimony  and legal  argument  based upon that  testimony.  The parties
subsequently  presented expert testimony and submitted additional  briefing.  On
April 29,  2003,  our motion for  summary  judgment of  non-infringement  of all
asserted  claims  was  granted,  plaintiffs'  motion  for  summary  judgment  of
infringement  was  denied  and the case was  ordered  closed.  On May 12,  2003,
Plaintiffs filed a Notice of Appeal regarding this decision to the U.S. Court of
Appeals for the Federal Circuit.

Our Stock Price Has Been And May Continue To Be Volatile, And Your Investment In
Our Stock Could Decline In Value Or Fluctuate Significantly.

The market prices for securities of biotechnology and  pharmaceutical  companies
have  historically  been highly  volatile,  and the market has from time to time
experienced  significant price and volume fluctuations that are unrelated to the
operating  performance of particular  companies.  The market price of our common
stock has fluctuated over a wide range and may continue to fluctuate for various
reasons, including, but not limited to, announcements concerning our competitors
or us regarding:

     -    results of clinical trials;

     -    technological innovations or new commercial products;

     -    changes in  governmental  regulation  or the status of our  regulatory
          approvals or applications;

                                      -16-

     -    changes in earnings;

     -    changes in health care policies and practices;

     -    developments or disputes concerning proprietary rights;

     -    litigation  or  public  concern  as to  safety  of the  our  potential
          products; and

     -    changes in general market conditions.

These  fluctuations may be exaggerated if the trading volume of our common stock
is low. These  fluctuations  may or may not be based upon any of our business or
operating results. Our common stock may experience similar or even more dramatic
price and volume fluctuations which may continue indefinitely.

The following table sets forth the high and low sale prices for our common stock
for each of the quarters in the period beginning April 1, 2000 through March 31,
2003  as  reported  on the  Nasdaq  National  Market,  and as  adjusted  for our
one-for-ten reverse stock split effected October 25, 2002:

   Quarter Ended                        High                    Low
   -------------                        ----                    ---
June 30, 2000                         $106.25                  $38.13
September 30, 2000                    $113.75                  $55.00
December 31, 2000                      $71.88                  $20.00
March 31, 2001                         $65.63                  $23.13
June 30, 2001                          $61.00                  $21.88
September 30, 2001                     $53.90                  $19.00
December 31, 2001                      $45.50                  $20.50
March 31, 2002                         $34.70                  $21.10
June 30, 2002                          $22.40                   $9.10
September 30, 2002                     $11.50                   $3.20
December 31, 2002                       $8.44                   $2.68
March 31, 2003                          $3.90                   $2.51

We Have Adopted  Various  Anti-Takeover  Provisions  Which May Affect The Market
Price Of Our Common Stock.

Our Board of Directors has the authority,  without further action by the holders
of common stock, to issue from time to time, up to 5,400,000 shares of preferred
stock in one or more classes or series, and to fix the rights and preferences of
the  preferred  stock.  Pursuant  to these  provisions,  we have  implemented  a
stockholder  rights plan by which one preferred stock purchase right is attached
to each share of common stock, as a means to deter coercive takeover tactics and
to prevent an acquirer  from  gaining  control of us without  some  mechanism to
secure a fair price for all of our stockholders if an acquisition was completed.
These  rights  will be  exercisable  if a person  or group  acquires  beneficial
ownership  of 20% or more of our  common  stock and can be made  exercisable  by
action of our board of directors  if a person or group  commences a tender offer
which would  result in such person or group  beneficially  owning 20% or more of
our common stock.  Each right will entitle the holder to buy one  one-thousandth
of a share of a new series of our junior participating  preferred stock for $20.
If any person or group becomes the beneficial owner of 20% or more of our common
stock (with certain  limited  exceptions),  then each right not owned by the 20%
stockholder  will  entitle its holder to  purchase,  at the right's then current
exercise price, common shares having a market value of twice the exercise price.
In addition,  if after any person has become a 20% stockholder,  we are involved
in a merger or other business combination  transaction with another person, each
right will entitle its holder (other than the 20%  stockholder) to purchase,  at
the right's then current exercise price,  common shares of the acquiring company
having a value of twice the right's then current exercise price.

                                      -17-



We are subject to provisions of Delaware corporate law which, subject to certain
exceptions,  will prohibit us from engaging in any "business combination" with a
person who,  together with  affiliates and  associates,  owns 15% or more of our
common stock for a period of three years following the date that the person came
to own 15% or more of our  common  stock  unless  the  business  combination  is
approved in a prescribed manner.

These   provisions  of  the   stockholder   rights  plan,  our   certificate  of
incorporation, and of Delaware law may have the effect of delaying, deterring or
preventing a change in control of Cytogen,  may  discourage  bids for our common
stock at a premium over market price and may adversely  affect the market price,
and the voting and other rights of the holders, of our common stock.

The Liquidity Of Our Common Stock Could Be Adversely Affected If We Are Delisted
From The Nasdaq National Market.

On August 14, 2002,  we announced  that we had  received  notification  from the
Nasdaq  Stock  Market,  Inc.  that our common stock had closed below the minimum
$1.00 per share  requirement  for the  previous 30  consecutive  trading days as
required under Marketplace Rule 4450(a)(5).  In accordance with Marketplace Rule
4450 (e)(2), we were provided with 90 calendar days, or until November 12, 2002,
to regain compliance by having the bid price for our common stock close at $1.00
or greater for a minimum period of 10 consecutive trading days.

On September  26, 2002,  we  announced  that our Board of Directors  unanimously
approved,  and recommended to our  stockholders,  a proposal that would give the
Board of  Directors  authority  to effect a reverse  stock  split of our  common
stock, at a ratio of up to one-for-ten at any time prior to December 31, 2002. A
special  meeting of our  stockholders  was held on October  25, 2002 to consider
such recommendation. Pursuant to the authority granted to our Board of Directors
at the special  meeting,  on October 25,  2002,  we  implemented  a  one-for-ten
reverse split of our outstanding and authorized shares of common stock.

We subsequently achieved compliance with Nasdaq Marketplace Rule 4450(a)(5), and
received a letter from Nasdaq  notifying us of such  compliance  on November 11,
2002.

We cannot  assure you that we will  continue  to maintain  compliance  with this
Marketplace  Rule, or any other Listing  Standards which may apply to us, and as
such, we may once again face  delisting from the Nasdaq  National  Market in the
future.  Specifically,  we cannot  assure  you that we will be able to  maintain
compliance  with the  minimum  equity  and  market  value of  listed  securities
requirements for continued listing on the Nasdaq National Market as set forth in
Marketplace Rule 4310(c)(2)(B).

In the event that we are unable  maintain  compliance  with all relevant  Nasdaq
listing  standards,  our  securities may be subject to delisting from the Nasdaq
National Market. If such delisting occurs, the market price and market liquidity
of our common stock may be adversely affected.

Alternatively,  if faced with such  delisting,  we may submit an  application to
transfer  the listing of our common  stock to the Nasdaq  SmallCap  Market.  The
Nasdaq SmallCap Market also has a $1.00 minimum bid price requirement.

If our common stock is delisted by Nasdaq, our common stock would be eligible to
trade on the OTC Bulletin Board maintained by Nasdaq,  another  over-the-counter
quotation  system,  or on the pink  sheets  where an  investor  may find it more
difficult to dispose of or obtain accurate  quotations as to the market value of
our common stock. In addition,  we would be subject to a rule promulgated by the


                                      -18-


Securities and Exchange  Commission  that, if we fail to meet criteria set forth
in such rule,  imposes various practice  requirements on broker-dealers who sell
securities governed by the rule to persons other than established  customers and
accredited  investors.  Consequently,  such rule may deter  broker-dealers  from
recommending or selling our common stock, which may further affect the liquidity
of our common stock.

Delisting  from Nasdaq will make  trading our common  stock more  difficult  for
investors,  potentially leading to further declines in our share price. It would
also make it more difficult for us to raise additional  capital.  Further, if we
are delisted we would also incur  additional  costs under state blue sky laws in
connection with any sales of our securities.  These  requirements could severely
limit  the  market  liquidity  of  our  common  stock  and  the  ability  of our
shareholders to sell our common stock in the secondary market.

A Large Number Of Our Shares Are  Eligible  For Future Sale Which May  Adversely
Impact The Market Price Of Our Common Stock.

A large number of shares of our common stock are already  outstanding,  issuable
upon exercise of options and warrants,  or the achievement of certain milestones
under previously  completed  acquisitions and may be eligible for resale,  which
may adversely  affect the market price of our common stock.  As of June 18, 2003
we had 9,818,755 shares of common stock outstanding, which number of shares: (i)
includes  an  aggregate  of 241  shares  of  common  stock to be issued to prior
holders of  securities  of CytoRad  Incorporated  and  Cellcor,  Inc.,  which we
acquired in 1995, upon each such holders respective exchange of such securities;
(ii)  excludes  50,000  shares  of  common  stock  previously  issued  by us and
currently held in escrow pending release,  upon certain conditions,  to Advanced
Magnetics, who currently maintains voting control of such securities;  and (iii)
excludes 28,589 shares  previously  issued by us and currently held for issuance
by the  custodian  of our  Employee  Stock  Purchase  Plan  to the  participants
thereunder,  in the event they elect to  purchase  such  shares.  An  additional
392,715  shares of common  stock are issuable  upon the exercise of  outstanding
stock options and an additional 322,153 shares of common stock are issuable upon
the exercise of  outstanding  warrants,  including  the  warrants  issued to the
selling  stockholders  in this  prospectus.  Substantially  all of  such  shares
subject to  outstanding  options and warrants  will,  when issued upon  exercise
thereof,  be available  for immediate  resale in the public  market  pursuant to
either a currently effective  registration statement under the Securities Act of
1933, as amended, or pursuant to Rule 144 or Rule 701 promulgated thereunder. In
addition,  there are 167,951  additional  shares of common  stock  reserved  for
future issuance under our current stock options plans,  3,630 additional  shares
of  common  stock  reserved  for  issuance  under  our  401(k)  Plan and  22,751
additional  shares of common stock  reserved for the future  issuance  under our
employee  bonus plan.  All such reserved  shares have been  registered  with the
Securities and Exchange Commission pursuant to currently effective  registration
statements.  In addition,  there are 95,153  additional  shares of common stock,
subject to certain adjustments,  reserved for future issuance in connection with
the issuance of a convertible promissory note, having a seven (7) year maturity,
to ELAN Corporation, plc in August 1998.

In connection  with our  acquisition of Prostagen,  Inc. in June 1999, we issued
205,000  unregistered  shares of our common  stock to the then  stockholders  of
Prostagen, which shares may be sold from time to time pursuant to Rule 144 under
the Securities Act. Such stockholders  also have certain piggyback  registration
rights with  respect to these  shares of common  stock.  An  additional  127,699
shares  have  been  issued  in  2002  and  were  subsequently  registered  on  a
registration  statement on Form S-3. An additional $2.0 million worth of Cytogen
common stock,  which we are obligated to register  under the  Securities  Act of
1933, as amended,  may be issued if certain  milestones are achieved in the PSMA
development programs.

On October 25, 2001,  we filed with the  Securities  and  Exchange  Commission a
shelf registration statement on Form S-3 covering one million (1,000,000) shares
of our common stock.  297,066 and 416,670 of such registered  shares were issued
to the State of Wisconsin  Investment Board in private offering  transactions in
each of January 2002 and June 2002, respectively.


                                      -19-


Availability  of a significant  number of additional  shares of our common stock
could depress the price of our common stock.

Because  We Do Not  Intend  to Pay Any Cash  Dividends  On Our  Shares of Common
Stock,  Our  Stockholders  Will Not Be Able to Receive a Return on Their  Shares
Unless They Sell Them.

We have never paid or declared  any cash  dividends on our common stock or other
securities and intend to retain any future  earnings to finance the  development
and expansion of our business. We do not anticipate paying any cash dividends on
our  common  stock in the  foreseeable  future.  Unless  we pay  dividends,  our
stockholders  will not be able to receive a return on their  shares  unless they
sell them.

                SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

         This  prospectus  includes or incorporates  forward-looking  statements
within the meaning of Section 27A of the  Securities Act of 1933 and Section 21E
of the Securities Exchange Act of 1934, as amended.  All statements,  other than
statements of historical  facts,  included or  incorporated  in this  prospectus
regarding our strategy, future operations,  financial position, future revenues,
projected   costs,   prospects,   plans  and   objectives  of   management   are
forward-looking  statements.  The words "anticipates,"  "believes," "estimates,"
"expects,"  "intends," "may," "plans,"  "projects,"  "will," "would" and similar
expressions are intended to identify  forward-looking  statements,  although not
all  forward-looking  statements  contain  these  identifying  words.  We cannot
guarantee  that we actually will achieve the plans,  intentions or  expectations
disclosed  in our  forward-looking  statements  and you should  not place  undue
reliance  on our  forward-looking  statements.  Actual  results or events  could
differ materially from the plans,  intentions and expectations  disclosed in the
forward-looking  statements we make. We have included  important  factors in the
cautionary statements included or incorporated in this prospectus,  particularly
under the heading "Risk Factors",  that we believe could cause actual results or
events to differ  materially from the  forward-looking  statements that we make.
Our forward-looking statements do not reflect the potential impact of any future
acquisitions,  mergers, dispositions, joint ventures or investments we may make.
We do not assume any obligation to update any forward-looking statements.

         You should not unduly rely on forward-looking  statements  contained or
incorporated  by reference in this  prospectus.  Actual  results or outcomes may
differ materially from those predicted in our forward-looking  statements due to
the risks and  uncertainties  inherent in our  business,  including  among other
items, risks and uncertainties in:

     -    our ability to successfully execute our business and financial plans;

     -    our  ability  to compete  successfully  against  direct  and  indirect
          competitors;

     -    our ability to access the capital  markets in the near term and in the
          future to support our operations and for continued funding of existing
          projects  and for the  pursuit of new  projects  and to  maintain  the
          listing of our common stock on the Nasdaq National Market;

     -    our  ability to  successfully  develop and  commercialize  in-licensed
          products such as NMP22  BladderChek,  including  programs  designed to
          facilitate the use of our products, such as the Partners in Excellence
          or PIE Program;

     -    our ability to establish and  successfully  complete  clinical  trials
          where required for product approval;

     -    our ability to  determine  and  implement  the  appropriate  strategic
          initiative for our AxCell Biosciences subsidiary;

     -    our ability to obtain foreign regulatory approvals for products and to
          establish  marketing  arrangements  in  countries  where  approval  is
          obtained;

     -    the timing and results of clinical studies and regulatory approvals;


                                      -20-

     -    demonstration over time of the efficacy and safety of our products;

     -    our ability to develop new products;

     -    the degree of competition from existing or new products;

     -    our ability to protect our intellectual  property,  including  patents
          and know-how;

     -    the ability of Advanced Magnetics to satisfy the conditions  specified
          by the FDA regarding approval to market Combidex in the United States;

     -    the  ability  to  attract  and retain  personnel  needed for  business
          operations and strategic plans;

     -    shifts in the  regulatory  environment  affecting sale of our products
          such as third-party payor  reimbursement  issues and dependence on our
          partners for development of certain projects;

     -    the ability of us to obtain  proper  financing to reacquire the rights
          to market  Quadramet  in North  America and South  America from Berlex
          Laboratories, Inc.;

     -    the  ability to attract and  maintain,  and the  ultimate  success of,
          strategic  partnering  arrangements,  collaborations,  and acquisition
          candidates;

     -    our ability to successfully  commercialize  products through our joint
          venture,    PSMA    Development    Company,    LLC,   with   Progenics
          Pharmaceuticals, Inc;

     -    competitive products and technologies; and

     -    price pressure.

         You should read and interpret any  forward-looking  statements together
with the following documents:

     -    our most recent Annual Report on Form 10-K, as amended;

     -    our most recent quarterly report of Form 10-Q;

     -    the risk factors  contained in this prospectus under the caption "Risk
          Factors"; and

     -    our other filings with the Securities and Exchange Commission.

         Any forward-looking  statement speaks only as of the date on which that
statement is made. We will not update any  forward-looking  statement to reflect
events or  circumstances  that occur after the date on which such  statement  is
made.

                                 USE OF PROCEEDS

         We will not receive any proceeds from the sale of shares by the selling
stockholders.

         The  selling  stockholders  will  pay any  underwriting  discounts  and
commissions  and expenses  incurred by the selling  stockholders  for brokerage,
accounting,  tax or legal services or any other expenses incurred by the selling
stockholders in disposing of the shares.  We will bear all other costs, fees and
expenses  incurred in effecting the  registration  of the shares covered by this
prospectus,  including,  without  limitation,  all registration and filing fees,
Nasdaq listing fees and fees and expenses of our counsel and our accountants.


                                      -21-

                              SELLING STOCKHOLDERS

         On June 6, 2003, we entered into a Securities  Purchase  Agreement with
certain  institutional  investors pursuant to which we issued and sold 1,052,632
shares of our common  stock at $4.75 per share and issued  warrants  to purchase
315,790  shares of our common  stock at an exercise  price of $6.91 per share to
the  investors.  Pursuant  to the above  private  placement,  we entered  into a
Registration Rights Agreement with the institutional investors which requires us
to register on a Form S-3,  the shares  issued to the  investors  and the shares
issuable upon exercise of the warrants.

         The following table sets forth, to our knowledge,  certain  information
about the selling stockholders as of June 18, 2003.

         Beneficial  ownership is determined in accordance with the rules of the
SEC, and includes voting or investment  power with respect to shares.  Shares of
common stock  issuable  under stock  options and warrants  that are  exercisable
within 60 days after June 18,  2003 are deemed  outstanding  for  computing  the
percentage  ownership of the person holding the options and warrants but are not
deemed  outstanding for computing the percentage  ownership of any other person.
Unless  otherwise  indicated  below, to our knowledge,  all persons named in the
table have sole  voting and  investment  power with  respect to their  shares of
common  stock,  except  to the  extent  authority  is shared  by  spouses  under
applicable law. The inclusion of any shares in this table does not constitute an
admission of beneficial ownership for the person named below.



                                                                       Number of
                                     Shares of Common Stock            Shares of         Shares of Common Stock
    Name of Selling               Beneficially Owned Prior to        Common Stock       to be Beneficially Owned
      Stockholder                          Offering (1)            Being Offered(1)         After Offering (1)
--------------------------        -----------------------------    ----------------    ---------------------------
                                     Number      Percentage (2)                         Number      Percentage (2)
--------------------------        -----------    --------------    ----------------    --------     --------------
                                                                                            
Bonanza Master Fund Ltd.           684,211(3)         6.86%            684,211             0               *

BayStar Capital II LP              684,211(3)         6.86%            684,211             0               *


--------------------------
* Less than one percent.

(1)  Wedo not know  when or in what  amounts  a  selling  stockholder  may offer
     shares for sale. The selling  stockholders might not sell any or all of the
     shares offered by this  prospectus.  Because the selling  stockholders  may
     offer all or some of the shares  pursuant  to this  offering,  and  because
     there are currently no  agreements,  arrangements  or  understandings  with
     respect to the sale of any of the shares,  we cannot estimate the number of
     the shares that will be held by the selling  stockholders  after completion
     of the offering. However, for purposes of this table, we have assumed that,
     after  completion  of the  offering,  none of the  shares  covered  by this
     prospectus will be held by the selling stockholders.

(2)  Applicable  percentage  ownership  is based on  9,818,755  shares of common
     stock  outstanding as of June 18, 2003, plus any common stock equivalent or
     convertible  securities  held or  shares  beneficially  owned by each  such
     holder.

(3)  Includes 526,316 shares of common stock held by the selling stockholder and
     157,895  shares of common stock issuable to the selling  stockholders  upon
     exercise of a warrant held by the selling  stockholder.  The exercise price
     to purchase each share of common stock pursuant to the warrant is $6.91 per
     share.  Although the shares of common stock  issuable  upon exercise of the
     warrants  are  included  herein,  the terms of the  warrants  prohibit  the
     exercise  thereof  in the event  such  exercise  would  cause the  holder's
     beneficial ownership percentage to exceed 4.99%.


                                      -22-






                              PLAN OF DISTRIBUTION

         The  selling  stockholders  and any of their  pledgees,  assignees  and
successors-in-interest  may, from time to time,  sell any or all of their shares
of common stock on any stock exchange,  market or trading  facility on which the
shares  are traded or in private  transactions.  These  sales may be at fixed or
negotiated  prices.  The  selling  stockholders  may  use any one or more of the
following methods when selling shares:

     -    ordinary   brokerage   transactions  and  transactions  in  which  the
          broker-dealer solicits purchasers;

     -    block  trades  in which the  broker-dealer  will  attempt  to sell the
          shares as agent but may  position and resell a portion of the block as
          principal to facilitate the transaction;

     -    purchases  by  a   broker-dealer   as  principal  and  resale  by  the
          broker-dealer for its account;

     -    an  exchange   distribution  in  accordance  with  the  rules  of  the
          applicable exchange;

     -    privately negotiated transactions;

     -    settlement of short sales;

     -    broker-dealers  may  agree  with the  selling  stockholders  to sell a
          specified number of such shares at a stipulated price per share;

     -    a combination of any such methods of sale; and

     -    any other method permitted pursuant to applicable law.

         The selling  stockholders may also sell shares under Rule 144 under the
Securities Act, if available, rather than under this prospectus.

         Broker-dealers  engaged by the  selling  stockholders  may  arrange for
other  brokers-dealers  to  participate  in sales.  Broker-dealers  may  receive
commissions or discounts from the selling stockholders (or, if any broker-dealer
acts as agent for the purchaser of shares,  from the purchaser) in amounts to be
negotiated.  The  selling  stockholders  do not  expect  these  commissions  and
discounts to exceed what is customary in the types of transactions involved.

         The  selling  stockholders  may  from  time to time  pledge  or grant a
security  interest  in some or all of the shares of common  stock  owned by them
and,  if they  default in the  performance  of their  secured  obligations,  the
pledgees or secured  parties may offer and sell the shares of common  stock from
time to time under this  prospectus,  or under an amendment  to this  prospectus
under Rule  424(b)(3) or other  applicable  provision of the  Securities  Act of
1933,  as  amended,  amending  the list of selling  stockholders  to include the
pledgee,  transferee  or other  successors  in interest as selling  stockholders
under this prospectus.

         The  selling  stockholders  and any  broker-dealers  or agents that are
involved  in selling  the shares may be deemed to be  "underwriters"  within the
meaning of the Securities Act in connection with such sales. In such event,  any
commissions  received  by such  broker-dealers  or agents  and any profit on the
resale  of the  shares  purchased  by  them  may be  deemed  to be  underwriting
commissions or discounts under the Securities Act. The selling stockholders have
informed us that it does not have any  agreement or  understanding,  directly or
indirectly, with any person to distribute the common stock.


                                      -23-


         We  are  required  to  pay  all  fees  and  expenses  incident  to  the
registration of the shares. We have agreed to indemnify the selling stockholders
against certain losses, claims,  damages and liabilities,  including liabilities
under the Securities Act.

                                  LEGAL MATTERS

         The  validity  of the shares of common  stock  offered  hereby has been
passed upon by Hale and Dorr LLP, Princeton, New Jersey.

                       WHERE YOU CAN FIND MORE INFORMATION

         We file reports, proxy statements and other documents with the SEC. You
may read and copy any  document we file at the SEC's  public  reference  room at
Judiciary Plaza Building,  450 Fifth Street, N.W., Room 1024,  Washington,  D.C.
20549.  You  should  call  1-800-SEC-0330  for more  information  on the  public
reference  room. Our SEC filings are also available to you on the SEC's Internet
site at http://www.sec.gov.

         This prospectus is part of a registration  statement that we filed with
the  SEC.  The  registration  statement  contains  more  information  than  this
prospectus  regarding us and our common stock,  including  certain  exhibits and
schedules.  You can obtain a copy of the registration  statement from the SEC at
the address listed above or from the SEC's Internet site.

                      INFORMATION INCORPORATED BY REFERENCE

         The SEC requires us to "incorporate"  into this prospectus  information
that we file with the SEC in other  documents.  This means that we can  disclose
important  information to you by referring to other  documents that contain that
information.  The information incorporated by reference is considered to be part
of this  prospectus.  Information  contained in this  prospectus and information
that we file with the SEC in the future and  incorporate  by  reference  in this
prospectus automatically updates and supersedes previously filed information. We
incorporate  by reference the documents  listed below and any future  filings we
make with the SEC under  Sections  13(a),  13(c),  14 or 15(d) of the Securities
Exchange  Act of  1934,  prior  to the sale of all the  shares  covered  by this
prospectus.

     (1)  Our Annual  Report on Form 10-K for the year ended  December 31, 2002,
          as filed with the  Securities  and  Exchange  Commission  on March 31,
          2003;

     (2)  Amendment  Number 1 to our Annual  Report on Form  10-K/A for the year
          ended  December 31, 2002,  as filed with the  Securities  and Exchange
          Commission on March 31, 2003;

     (3)  Our Current Report on Form 8-K, dated April 8, 2003, as filed with the
          Securities and Exchange Commission on April 9, 2003;

     (4)  Our Current  Report on Form 8-K, dated May 14, 2003, as filed with the
          Securities and Exchange Commission on May 14, 2003;

     (5)  Our Quarterly Report on Form 10-Q for the period ended March 31, 2003,
          as filed with the Securities and Exchange Commission on May 14, 2003;


                                      -24-

     (6)  Our Current  Report on Form 8-K, dated June 6, 2003, as filed with the
          Securities and Exchange Commission on June 9, 2003;

     (7)  The  description  of our common stock  contained  in our  Registration
          Statement on Form 8-A, as  supplemented by the disclosure set forth in
          Exhibit 3.1 to our Form 10-Q  Quarterly  Report for the quarter  ended
          June 30, 2000 and Exhibit 3 to our Form 10-Q Quarterly  Report for the
          quarter ended June 30, 1996;

     (8)  The description of our Series C Junior  Participating  Preferred Stock
          contained  in Exhibit 1 to our  Current  Report on Form 8-K filed with
          the Securities and Exchange Commission on June 24, 1998; and

     (9)  All of our  filings  pursuant  to the  Exchange  Act after the date of
          filing the initial  registration  statement and prior to effectiveness
          of the registration statement.

         You may  request a copy of these  documents,  which will be provided to
you at no cost,  by  writing  or  telephoning  us using  the  following  contact
information:

                           Cytogen Corporation
                           650 College Road East, 3rd Floor
                           Princeton, New Jersey 08540
                           Attention:  Corporate Communications
                           Telephone:  609-750-8200

         You  should  rely  on the  information  incorporated  by  reference  or
provided in this prospectus or any prospectus supplement. We have not authorized
anyone  else to provide  you with  different  information.  We are not making an
offer of these securities in any jurisdiction  where the offer is not permitted.
You should not assume that the  information in this prospectus or any prospectus
supplement  is accurate as of any date other than the date on the front of these
documents.


                                      -25-




                                     PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14.      Other Expenses of Issuance and Distribution.

         The following  table sets forth the various  expenses to be incurred in
connection  with the sale and  distribution of the securities  being  registered
hereby,  all  of  which  will  be  borne  by  Cytogen  Corporation  (except  any
underwriting  discounts  and  commissions  and expenses  incurred by the selling
stockholders  for  brokerage,  accounting,  tax or legal  services  or any other
expenses incurred by the selling  stockholders in disposing of the shares).  All
amounts  shown are  estimates  except the  Securities  and  Exchange  Commission
registration fee.

    Filing Fee - Securities and Exchange Commission ........    $ 822.54

    Legal fees and expenses.................................   $15,000.00

    Accounting fees and expenses............................   $12,000.00
                                                               ==========
             Total Expenses.................................   $27,822.54

Item 15.      Indemnification of Directors and Officers.

         Subsection (a) of Section 145 of the Delaware  General  Corporation Law
empowers a  corporation  to indemnify  any person who was or is threatened to be
made a party to any threatened, pending or completed action, suit or proceeding,
whether civil,  criminal,  administrative or investigative (other than an action
by or in the right of the  corporation)  by reason of the fact that he or she is
or was a director,  officer, employee or agent of the corporation,  or is or was
serving at the request of the  corporation as a director,  officer,  employee or
agent  of  another  corporation,  partnership,  joint  venture,  trust  or other
enterprise,  against expenses (including attorneys' fees), judgments,  fines and
amounts paid in  settlement  actually and  reasonably  incurred by him or her in
connection with such action, suit or proceeding if he or she acted in good faith
and in a manner he or she  reasonably  believed  to be in or not  opposed to the
best interests of the  corporation,  and, with respect to any criminal action or
proceeding, had no reasonable cause to believe his or her conduct was unlawful.

         Subsection  (b) of Section 145 empowers a corporation  to indemnify any
person  who  was or is a  party  or is  threatened  to be  made a  party  to any
threatened,  pending  or  completed  action  or suit by or in the  right  of the
corporation  to procure a judgment in its favor by reason of the fact that he or
she is or was a director,  officer, employee or agent of the corporation,  or is
or was  serving  at the  request  of the  corporation  as a  director,  officer,
employee or agent of another corporation,  partnership,  joint venture, trust or
other  enterprise,  against  expenses  (including  attorneys' fees) actually and
reasonably  incurred by him or her in connection  with the defense or settlement
of such  action or suit if he or she  acted in good  faith and in a manner he or
she  reasonably  believed to be in or not opposed to the best  interests  of the
corporation and except that no  indemnification  shall be made in respect of any
claim,  issue or matter as to which such person  shall have been  adjudged to be
liable  to the  corporation  unless  and only to the  extent  that the  Court of
Chancery or the court in which such action or suit was brought  shall  determine
upon application that,  despite the adjudication of liability but in view of all
of the circumstances of the case, such person is fairly and reasonably  entitled
to indemnity for such  expenses  which the Court of Chancery or such other court
shall deem proper.


                                      II-1


         Section 145 further  provides  that to the extent a director or officer
of a  corporation  has been  successful  in the defense of any  action,  suit or
proceeding referred to in subsection (a) and (b) or in the defense of any claim,
issue or  matter  therein,  he or she  shall  be  indemnified  against  expenses
(including  attorneys'  fees) actually and reasonably  incurred by him or her in
connection therewith; that the indemnification provided by Section 145 shall not
be deemed  exclusive of any other rights to which the  indemnified  party may be
entitled; and that the scope of indemnification extends to directors,  officers,
employees, or agents of a constituent corporation absorbed in a consolidation or
merger and persons  serving in that  capacity at the request of the  constituent
corporation for another. Section 145 also empowers a corporation to purchase and
maintain insurance on behalf of a director or officer of the corporation against
any liability  asserted against him or her or incurred by him or her in any such
capacity  or  arising  out of his or her  status  as  such  whether  or not  the
corporation  would  have  the  power  to  indemnify  him  or  her  against  such
liabilities under Section 145.

         Section  102(b)(7) of the Delaware  General  Corporation  Law enables a
corporation in its certificate of incorporation to limit the personal  liability
of members of its board of directors  for  violation  of a director's  fiduciary
duty of care. This section does not, however,  limit the liability of a director
for breaching his or her duty of loyalty, failing to act in good faith, engaging
in intentional misconduct or knowingly violating a law, authorizing a payment of
a dividend or approving a stock  repurchase  in violation of Delaware  Corporate
Law or from any transaction in which the director  derived an improper  personal
benefit.  This  section  also will have no  effect on claims  arising  under the
federal securities laws.

         The Company's Certificate of Incorporation and By-Laws provide that the
Company shall indemnify  officers and directors and, to the extent  permitted by
the Board of Directors,  employees and agents of the Company, to the full extent
permitted  by and in the  manner  permissible  under  the  laws of the  State of
Delaware.  In addition,  the By-Laws  permit the Board of Directors to authorize
the Company to purchase and maintain  insurance  against any director,  officer,
employee or agent of the Company arising out of his capacity as such.

         Cytogen  has  obtained  liability  insurance  for  the  benefit  of its
directors  and officers  which  provides  coverage  for losses of directors  and
officers for  liabilities  arising out of claims  against such persons acting as
directors or officers of Cytogen (or any  subsidiary  thereof) due to any breach
of duty, neglect,  error,  misstatement,  misleading statement,  omission or act
done by such directors and officers, except as prohibited by law.

Item 16.      Exhibits.

      (a)      Exhibits

               5.1**    Opinion of Hale and Dorr LLP.

               23.1**   Consent of Hale and Dorr LLP (To be included in
                         Exhibit 5.1).

               24.1*    Power of Attorney. (Included on signature page).

----------
*     Filed herewith.

**    To be filed by amendment.


                                      II-2


Item 17.      Undertakings.

         The undersigned Registrant hereby undertakes:

     (1) To file,  during any period in which  offers or sales are being made, a
post-effective amendment to this Registration Statement:

     (i)  To  include  any  prospectus  required  by  Section  10(a)(3)  of  the
          Securities Act of 1933, as amended (the "Securities Act");

     (ii) To reflect in the  prospectus  any facts or events  arising  after the
          effective  date of this  Registration  Statement  (or the most  recent
          post-effective  amendment  thereof)  which,  individually  or  in  the
          aggregate, represent a fundamental change in the information set forth
          in this Registration  Statement.  Notwithstanding  the foregoing,  any
          increase  or decrease  in volume of  securities  offered (if the total
          dollar  value of  securities  offered  would not exceed that which was
          registered)  and  any  deviation  from  the  low  or  high  end of the
          estimated  maximum  offering  range  may be  reflected  in the form of
          prospectus  filed with the  Commission  pursuant to Rule 424(b) if, in
          the aggregate,  the changes in volume and price represent no more than
          20% change in the maximum  aggregate  offering  price set forth in the
          "Calculation of Registration Fee" table in the effective  Registration
          Statement; and

     (iii)To  include  any  material  information  with  respect  to the plan of
          distribution not previously  disclosed in this Registration  Statement
          or any  material  change  to such  information  in  this  Registration
          Statement;

provided,  however,  that  paragraphs  (1)(i)  and  (1)(ii)  do not apply if the
information  required  to be  included in a  post-effective  amendment  by those
paragraphs  is  contained  in periodic  reports  filed with or  furnished to the
Commission  by the  Registrant  pursuant  to Section 13 or Section  15(d) of the
Securities  Exchange Act of 1934,  as amended  (the  "Exchange  Act"),  that are
incorporated by reference in this Registration Statement.

     (2)  That,  for  the  purposes  of  determining  any  liability  under  the
Securities  Act,  each  post-effective  amendment  shall be  deemed  to be a new
registration  statement  relating to the  securities  offered  therein,  and the
offering of such  securities  at the time shall be deemed to be the initial bona
fide offering thereof.

     (3) To remove from registration by means of a post-effective  amendment any
of the securities being registered which remain unsold at the termination of the
offering.

         The Registrant  hereby undertakes that, for purposes of determining any
liability  under the  Securities  Act,  each filing of the  Registrant's  annual
report  pursuant  to  Section  13(a) or 15(d) of the  Exchange  Act (and,  where
applicable,  each filing of an employee benefit plan's annual report pursuant to
Section  15(d) of the Exchange  Act) that is  incorporated  by reference in this
Registration  Statement  shall  be  deemed  to be a new  registration  statement
relating to the securities offered therein,  and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

         Insofar as indemnification for liabilities arising under the Securities
Act may be  permitted to  directors,  officers  and  controlling  persons of the
Company  pursuant  to  the  indemnification   provisions  described  herein,  or
otherwise,  the Company has been advised  that in the opinion of the  Securities
and  Exchange  Commission  such  indemnification  is  against  public  policy as
expressed in the Securities Act and is, therefore,  unenforceable.  In the event


                                      II-3


that a claim  for  indemnification  against  such  liabilities  (other  than the
payment by the  Company of expenses  incurred or paid by a director,  officer or
controlling person of the Company in the successful defense of any action,  suit
or proceeding) is asserted by such  director,  officer or controlling  person in
connection with the securities being registered, the Company will, unless in the
opinion of its counsel  the matter has been  settled by  controlling  precedent,
submit  to a  court  of  appropriate  jurisdiction  the  question  whether  such
indemnification  by it is against  public policy as expressed in the  Securities
Act and will be governed by the final adjudication of such issue.


                                      II-4






                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the  requirements  for  filing  on  Form  S-3 and has  duly  caused  this
Registration Statement to be signed on its behalf by the undersigned,  thereunto
duly authorized, in the City of Princeton, State of New Jersey, on July 3, 2003.

                                     CYTOGEN CORPORATION


                                     By:   /s/ Michael D. Becker
                                        -------------------------------------
                                        Michael D. Becker
                                        President and Chief Executive Officer







                        SIGNATURES AND POWER OF ATTORNEY

         We, the  undersigned  officers and  directors  of Cytogen  Corporation,
hereby  severally  constitute and appoint  Michael D. Becker and Thu A. Dang and
each of them  singly,  our true and lawful  attorneys  with full power to any of
them,  and to each of  them  singly,  to  sign  for us and in our  names  in the
capacities indicated below the Registration Statement on Form S-3 filed herewith
and any and all pre-effective and post-effective amendments to said Registration
Statement  and  generally  to do all such  things in our name and  behalf in our
capacities as officers and  directors to enable  Cytogen  Corporation  to comply
with  the  provisions  of the  Securities  Act of  1933,  as  amended,  and  all
requirements  of the Securities and Exchange  Commission,  hereby  ratifying and
confirming our signatures as they may be signed by our said attorneys, or any of
them, to said Registration Statement and any and all amendments thereto.

         Pursuant to the requirements of the Securities Act of 1933, as amended,
this  Registration  Statement  has been signed by the  following  persons in the
capacities and on the dates indicated.



            Signature                               Title                            Date
-------------------------------     --------------------------------------      --------------

                                                                          
/s/ Michael D. Becker               President, Chief Executive Officer and      July 3, 2003
-------------------------------     Director (Principal Executive Officer)
Michael D. Becker

/s/ Thu A. Dang                     Vice President, Finance (Principal          July 3, 2003
-------------------------------     Financial and Accounting Officer)
Thu A. Dang

/s/ John E. Bagalay, Jr             Director                                    July 3, 2003
-------------------------------
John E.  Bagalay, Jr.

/s/ Allen Bloom                     Director                                    July 3, 2003
-------------------------------
Allen Bloom

/s/ Stephen K. Carter               Director                                    July 3, 2003
-------------------------------
Stephen K.  Carter

/s/ James A. Grigsby                Director                                    July 3, 2003
-------------------------------
James A. Grigsby

/s/ Robert F. Hendrickson           Director                                    July 3, 2003
-------------------------------
Robert F.  Hendrickson

/s/ Kevin G. Lokay                  Director                                    July 3, 2003
-------------------------------
Kevin G. Lokay

/s/ H. Joseph Reiser                Director                                    July 3, 2003
-------------------------------
H. Joseph Reiser




                                  EXHIBIT INDEX


  EXHIBIT NUMBER                         DESCRIPTION
  --------------    -----------------------------------------------------------
     **5.1          Opinion of Hale and Dorr LLP.

     **23.1         Consent of Hale and Dorr LLP (To be included in Exhibit 5.1)

      *24.1         Power of Attorney (included on signature page).


*  Filed herewith.

** To be filed by amendment.