WASHINGTON, D.C. 20549

IN THE MATTER OF                                            INITIAL CERTIFICATE
AMEREN CORPORATION, ET AL.                                  PURSUANT TO
                                                            RULE 24
File No. 70-10220

(Public Utility Holding Company Act of 1935)

     This Certificate of Notification pursuant to Rule 24 under the Public
Utility Holding Company Act of 1935, as amended (the "Act"), is filed by Ameren
Corporation ("Ameren"), a registered holding company, in connection with
Ameren's acquisition of all of the issued and outstanding common stock ("Common
Shares") of Illinois Power Company ("Illinois Power") from Illinova Corporation
("Illinova") and the issued and outstanding shares of preferred stock
("Preferred Shares") of Illinois Power that are owned by Illinova, as authorized
by order of the Securities and Exchange Commission (the "Commission") dated
September 27, 2004 (the "Order"), in this proceeding (Holding Co. Act Release
No. 27896). Ameren hereby certifies to the Commission pursuant to Rule 24 that,
on September 30, 2004: (i) Ameren acquired the Common Shares and the Preferred
Shares, together with the 20% interest in the common stock of Electric Energy,
Inc. that was held by Illinova Generating Company, for $2.3 billion consisting
of assumption of the existing outstanding indebtedness of Illinois Power in the
amount of $1.823 billion, $100 million in cash placed into an escrow account
pending resolution of certain contingent environmental obligations of Illinois
Power and certain its affiliates, with the balance paid in cash, and (ii)
Illinois Power entered into the Ameren System Utility Money Pool Agreement and a
Fuel and Natural Gas Services Agreement with its associate company, Ameren
Energy Fuels and Services Company.

     Certificates pursuant to Rule 24 with respect to completion of the other
transactions authorized by the Commission in this proceeding will be filed on a
quarterly basis as provided in the Order.

     A "past tense" opinion of counsel is filed as Exhibit F hereto.


     Pursuant to the requirements of the Act, the undersigned company has duly
caused this certificate to be signed on its behalf by the undersigned thereunto
duly authorized.

                                            Ameren Corporation

                                            By: /s/ Jerre E. Birdsong
                                            Name:   Jerre E. Birdsong
                                            Title:  Vice President and Treasurer

Dated:  October 4, 2004