Exhibit 32.1

SECTION 1350 CERTIFICATION

OF PRINCIPAL EXECUTIVE OFFICER

OF AMEREN CORPORATION

(required by Section 906 of the

Sarbanes-Oxley Act of 2002)

In connection with the report on Form 10-Q for the quarterly period ended September 30, 2004 of Ameren Corporation (the “Company”) as filed with the Securities and Exchange Commission on the date hereof (the "Form 10-Q"), I, Gary L. Rainwater, chief executive officer of the Company, certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that:

(1)   The Form 10-Q fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m or 78o(d)); and

(2)   The information contained in the Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: November 9, 2004

/s/ Gary L. Rainwater  

Gary L. Rainwater

Chairman, President and

Chief Executive Officer

(Principal Executive Officer)