SECURITIES & EXCHANGE COMMISSION
                             Washington, D.C. 20549
                             ----------------------

                                 SCHEDULE 13GA*
                                 (Rule 13d-102)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
           TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED
                              PURSUANT TO 13d-2(b)

                         Affiliated Managers Group, Inc.
                                (Name of Issuer)

                                  Common Stock
                         (Title of Class of Securities)

                                    008252108
                                 (CUSIP Number)

                                December 31, 2002
             (Date of event which requires filing of this statement)


     Check the appropriate box to designate the rule pursuant to which this
Schedule 13G is filed:
     [ ] Rule 13d-1(b)
     [X] Rule 13d-1(c)
     [ ] Rule 13d-1(d)





                              (Page 1 of 12 Pages)
----------------
     *The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter the disclosures provided in a prior cover page.

     The information required in the remainder of this cover page shall not be
deemed to be "filed" for purposes of Section 18 of the Securities Exchange Act
of 1934 ("Act") or otherwise subject to the liabilities of that section of the
Act but shall be subject to all other provisions of the Act (however, see the
Notes).






CUSIP No. 008252108                 13GA                     Page 2 of 12 Pages
-------------------------------------------------------------------------------
     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)
                                          Lone Spruce, L.P.
-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
                                                             (a) [X]
                                                             (b) [ ]
-------------------------------------------------------------------------------
     (3)    SEC USE ONLY
-------------------------------------------------------------------------------
     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION
                              Delaware
-------------------------------------------------------------------------------
NUMBER OF      (5)  SOLE VOTING POWER
                                                   -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                                                   28,667
OWNED BY       ----------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                                                   -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                                                   28,667
-------------------------------------------------------------------------------
     (9)    AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
                                                   28,667
-------------------------------------------------------------------------------
     (10)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (9) EXCLUDES CERTAIN SHARES **               [ ]
-------------------------------------------------------------------------------
     (11)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (9)
                                                   0.1%
-------------------------------------------------------------------------------
     (12)   TYPE OF REPORTING PERSON **
                                                   PN
-------------------------------------------------------------------------------
                     ** SEE INSTRUCTIONS BEFORE FILLING OUT!






CUSIP No. 008252108                 13GA                     Page 3 of 12 Pages
-------------------------------------------------------------------------------
     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)
                                           Lone Balsam, L.P.
-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
                                                           (a)  [X]
                                                           (b)  [ ]
-------------------------------------------------------------------------------
     (3)    SEC USE ONLY
-------------------------------------------------------------------------------
     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION
                             Delaware
-------------------------------------------------------------------------------
NUMBER OF      (5)  SOLE VOTING POWER
                                                   -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                                                   62,911
OWNED BY       ----------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                                                   -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                                                   62,911
-------------------------------------------------------------------------------
     (9)    AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
                                                   62,911
-------------------------------------------------------------------------------
     (10)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (9) EXCLUDES CERTAIN SHARES **              [ ]
-------------------------------------------------------------------------------
     (11)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (9)
                                                   0.3%
-------------------------------------------------------------------------------
     (12)   TYPE OF REPORTING PERSON **
                                                   PN
-------------------------------------------------------------------------------
                     ** SEE INSTRUCTIONS BEFORE FILLING OUT!






CUSIP No. 008252108                 13GA                     Page 4 of 12 Pages
-------------------------------------------------------------------------------
     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)
                                          Lone Sequoia, L.P.
-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
                                                               (a)  [X]
                                                               (b)  [ ]
-------------------------------------------------------------------------------
     (3)    SEC USE ONLY
-------------------------------------------------------------------------------
     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION
                              Delaware
-------------------------------------------------------------------------------
NUMBER OF      (5)  SOLE VOTING POWER
                                                      -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                                                      52,558
OWNED BY       ----------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                                                      -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                                                      52,558
-------------------------------------------------------------------------------
     (9)    AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
                                                      52,558
-------------------------------------------------------------------------------
     (10)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (9) EXCLUDES CERTAIN SHARES **                  [ ]
-------------------------------------------------------------------------------
     (11)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (9)
                                                      0.2%
-------------------------------------------------------------------------------
     (12)   TYPE OF REPORTING PERSON **
                                                      PN
-------------------------------------------------------------------------------
                     ** SEE INSTRUCTIONS BEFORE FILLING OUT!






CUSIP No. 008252108                 13GA                     Page 5 of 12 Pages

-------------------------------------------------------------------------------
     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)
                                           Lone Pine Associates LLC
-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
                                                               (a)  [X]
                                                               (b)  [ ]
-------------------------------------------------------------------------------
     (3)    SEC USE ONLY
-------------------------------------------------------------------------------
     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION
                             Delaware
-------------------------------------------------------------------------------
NUMBER OF      (5)  SOLE VOTING POWER
                                                     -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                                                     144,136
OWNED BY       ----------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                                                     -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                                                     144,136
-------------------------------------------------------------------------------
     (9)    AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
                                                     144,136
-------------------------------------------------------------------------------
     (10)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (9) EXCLUDES CERTAIN SHARES **                  [ ]
-------------------------------------------------------------------------------
     (11)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (9)
                                                     0.7%
-------------------------------------------------------------------------------
     (12)   TYPE OF REPORTING PERSON **
                                                     OO
-------------------------------------------------------------------------------
                     ** SEE INSTRUCTIONS BEFORE FILLING OUT!






CUSIP No. 008252108                 13GA                     Page 6 of 12 Pages

-------------------------------------------------------------------------------
     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)
                                          Lone Pine Capital LLC
-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
                                                               (a)  [X]
                                                               (b)  [ ]
-------------------------------------------------------------------------------
     (3)    SEC USE ONLY
-------------------------------------------------------------------------------
     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION
                             Delaware
-------------------------------------------------------------------------------
NUMBER OF      (5)  SOLE VOTING POWER
                                                     -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                                                     652,164
OWNED BY       ----------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                                                     -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                                                     652,164
-------------------------------------------------------------------------------
     (9)    AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
                                                     652,164
-------------------------------------------------------------------------------
     (10)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (9) EXCLUDES CERTAIN SHARES **                  [ ]
-------------------------------------------------------------------------------
     (11)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (9)
                                                     3.0%
-------------------------------------------------------------------------------
     (12)   TYPE OF REPORTING PERSON **
                                                     IA
-------------------------------------------------------------------------------
                     ** SEE INSTRUCTIONS BEFORE FILLING OUT!






CUSIP No. 008252108                 13GA                     Page 7 of 12 Pages

-------------------------------------------------------------------------------
     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)
                                                  Stephen F. Mandel, Jr.
-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
                                                               (a)  [X]
                                                               (b)  [ ]
-------------------------------------------------------------------------------
     (3)    SEC USE ONLY
-------------------------------------------------------------------------------
     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION
                             United States
-------------------------------------------------------------------------------
NUMBER OF      (5)  SOLE VOTING POWER
                                                     -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                                                     796,300
OWNED BY       ----------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                                                     -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                                                     796,300
-------------------------------------------------------------------------------
     (9)    AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
                                                     796,300
-------------------------------------------------------------------------------
     (10)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (9) EXCLUDES CERTAIN SHARES **                 [ ]
-------------------------------------------------------------------------------
     (11)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (9)
                                                     3.7%
-------------------------------------------------------------------------------
     (12)   TYPE OF REPORTING PERSON **
                                                     IN
-------------------------------------------------------------------------------
                     ** SEE INSTRUCTIONS BEFORE FILLING OUT!






CUSIP No. 008252108                 13GA                     Page 8 of 12 Pages

Item 1(a).     Name of Issuer:

     The name of the issuer is Affiliated Managers Group, Inc. (the "Company").

Item 1(b).     Address of Issuer's Principal Executive Offices:

     The Company's principal executive offices are located at 600 Hale Street,
Prides Crossing, Massachusetts 01965.

Item 2(a).     Name of Person Filing:

     This statement is filed by:
          (i) Lone Spruce, L.P., a Delaware limited partnership ("Lone Spruce"),
              with respect to the shares of Common Stock (defined in Item 2(d)
              below) directly owned by it;
         (ii) Lone Balsam, L.P., a Delaware limited partnership ("Lone Balsam"),
              with respect to the shares of Common Stock directly owned by it;
        (iii) Lone Sequoia, L.P., a Delaware limited partnership ("Lone
              Sequoia"), with respect to the shares of Common Stock directly
              owned by it;
         (iv) Lone Pine Associates LLC, a Delaware limited liability company
              ("Lone Pine"), with respect to the shares of Common Stock
              directly owned by Lone Spruce, Lone Balsam and Lone Sequoia;
          (v) Lone Pine Capital LLC, a Delaware limited liability company
              ("Lone Pine Capital"), which serves as investment manager to Lone
              Cypress, Ltd., a Cayman Islands exempted company ("Lone
              Cypress"), with respect to the shares of Common Stock directly
              owned by Lone Cypress;
         (vi) Stephen F. Mandel, Jr. ("Mr. Mandel"), with respect to the shares
              of Common Stock directly owned by each of Lone Spruce, Lone
              Balsam, Lone Sequoia and Lone Cypress.

              The foregoing persons are hereinafter sometimes collectively
         referred to as the "Reporting Persons". Any disclosures herein with
         respect to persons other than the Reporting Persons are made on
         information and belief after making inquiry to the appropriate party.

Item 2(b).     Address of Principal Business Office or, if None, Residence:

     The address of the business office of each of the Reporting Persons is Two
Greenwich Plaza, Greenwich, Connecticut 06830.






CUSIP No. 008252108                 13GA                     Page 9 of 12 Pages

Item 2(c).     Citizenship:

     Lone Spruce, Lone Balsam and Lone Sequoia are limited partnerships
organized under the laws of the State of Delaware. Lone Pine Associates LLC and
Lone Pine Capital LLC are limited liability companies organized under the laws
of the State of Delaware. Mr. Mandel is a United States citizen.

Item 2(d).     Title of Class of Securities:

     Common Stock, $0.01 par value (the "Common Stock")

Item 2(e).  CUSIP Number:

     008252108

Item 3.   If this statement is filed pursuant to Rules 13d-1(b) or 13d-2(b)
or (c), check whether the person filing is a:

          (a)  [ ] Broker or dealer registered under Section 15 of the Act,

          (b)  [ ] Bank as defined in Section 3(a)(6) of the Act,

          (c)  [ ] Insurance Company as defined in Section 3(a)(19) of the Act,

          (d)  [ ] Investment Company registered under Section 8 of the
                   Investment Company Act of 1940,

          (e)  [ ] Investment Adviser in accordance with Rule
                   13d-1(b)(1)(ii)(E),

          (f)  [ ] Employee Benefit Plan or Endowment Fund in accordance with
                   Rule 13d-1(b)(1)(ii)(F),

          (g)  [ ] Parent Holding Company or control person in accordance with
                   Rule 13d-1(b)(1)(ii)(G),

          (h)  [ ] Savings Association as defined in Section 3(b) of the Federal
                   Deposit Insurance Act,

          (i)  [ ] Church Plan that is excluded from the definition of an
                   investment company under Section 3(c)(14) of the Investment
                   Company Act of 1940,

          (j)  [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

If this statement is filed pursuant to Rule 13d-1(c), check the box. [X]






CUSIP No. 008252108                 13GA                    Page 10 of 12 Pages

Item 4.   Ownership.

     A.   Lone Spruce, L.P.

          (a)  Amount beneficially owned: 28,667

          (b)  Percent of class: 0.1% The percentages used herein and in the
               rest of Item 4 are calculated based upon the 21,754,520 shares of
               Voting Common Stock issued and outstanding as of November 11,
               2002 as reported in the Company's Form 10-Q for the period ending
               September 30, 2002.
          (c)(i) Sole power to vote or direct the vote: -0-
            (ii) Shared power to vote or direct the vote: 28,667
           (iii) Sole power to dispose or direct the disposition: -0-
            (iv) Shared power to dispose or direct the disposition: 28,667

     B.   Lone Balsam, L.P.
          (a)  Amount beneficially owned: 62,911
          (b)  Percent of class: 0.3%
          (c)(i) Sole power to vote or direct the vote: -0-
            (ii) Shared power to vote or direct the vote: 62,911
           (iii) Sole power to dispose or direct the disposition: -0-
            (iv) Shared power to dispose or direct the disposition: 62,911

     C.   Lone Sequoia, L.P.
          (a)  Amount beneficially owned: 52,558
          (b)  Percent of class: 0.2%
          (c)(i) Sole power to vote or direct the vote: -0-
            (ii) Shared power to vote or direct the vote: 52,558
            (iii) Sole power to dispose or direct the disposition: -0-
            (iv) Shared power to dispose or direct the disposition: 52,558

     D.   Lone Pine Associates LLC
          (a)  Amount beneficially owned: 144,136
          (b)  Percent of class: 0.7%
          (c)(i) Sole power to vote or direct the vote: -0-
            (ii) Shared power to vote or direct the vote: 144,136
           (iii) Sole power to dispose or direct the disposition: -0-
            (iv) Shared power to dispose or direct the disposition: 144,136

     C.   Lone Pine Capital LLC
          (a)  Amount beneficially owned: 652,164
          (b)  Percent of class: 3.0%
          (c)(i) Sole power to vote or direct the vote: -0-
            (ii) Shared power to vote or direct the vote: 652,164
           (iii) Sole power to dispose or direct the disposition: -0-
            (iv) Shared power to dispose or direct the disposition: 652,164






CUSIP No. 008252108                 13GA                    Page 11 of 12 Pages

     D.   Stephen F. Mandel, Jr.
          (a)  Amount beneficially owned: 796,300
          (b)  Percent of class: 3.7%
          (c)(i) Sole power to vote or direct the vote: -0-
            (ii) Shared power to vote or direct the vote: 796,300
           (iii) Sole power to dispose or direct the disposition: -0-
            (iv) Shared power to dispose or direct the disposition: 796,300

Item 5.     Ownership of Five Percent or Less of a Class.

     If this statement is being filed to report the fact that as of the date
hereof the reporting person has ceased to be the beneficial owner of more than
five percent of the class of securities, check the following [x].

Item 6.     Ownership of More than Five Percent on Behalf of Another Person.

     Not applicable.

Item 7.     Identification and Classification of the Subsidiary Which Acquired
the Security Being Reported on by the Parent Holding Company.

     Not applicable.

Item 8.     Identification and Classification of Members of the Group.

     See Item 2.

Item 9.     Notice of Dissolution of Group.

     Not applicable.

Item 10.    Certification.

     Each of the Reporting Persons hereby makes the following certification:

          By signing below I certify that, to the best of my knowledge and
belief, the securities referred to above were not acquired and are not held for
the purpose of or with the effect of changing or influencing the control of the
issuer of the securities and were not acquired and are not held in connection
with or as a participant in any transaction having that purpose or effect.






CUSIP No. 008252108                 13GA                    Page 12 of 12 Pages

                                   SIGNATURES

         After reasonable inquiry and to the best of our knowledge and belief,
the undersigned certify that the information set forth in this statement is
true, complete and correct.

DATED:  February 13, 2003

                                             LONE SPRUCE, L.P.

                                             By:  Lone Pine Associates LLC,
                                                  General Partner

                                             By:  /s/ Stephen F. Mandel, Jr.
                                                  --------------------------
                                                  Stephen F. Mandel, Jr.
                                                  Managing Member

                                             LONE BALSAM, L.P.

                                             By:  Lone Pine Associates LLC,
                                                  General Partner

                                             By:  /s/ Stephen F. Mandel, Jr.
                                                  --------------------------
                                                  Stephen F. Mandel, Jr.
                                                  Managing Member

                                             LONE SEQUOIA, L.P.

                                             By:  Lone Pine Associates LLC,
                                                  General Partner

                                             By:  /s/ Stephen F. Mandel, Jr.
                                                  --------------------------
                                                  Stephen F. Mandel, Jr.
                                                  Managing Member

                                             LONE PINE ASSOCIATES LLC

                                             By:  /s/ Stephen F. Mandel, Jr.
                                                  --------------------------
                                                  Stephen F. Mandel, Jr.
                                                  Managing Member

                                             LONE PINE CAPITAL LLC

                                             By:  /s/ Stephen F. Mandel, Jr.
                                                  --------------------------
                                                  Stephen F. Mandel, Jr.
                                                  Managing Member

                                             STEPHEN F. MANDEL, JR.

                                             /s/ Stephen F. Mandel, Jr.
                                             -------------------------------