SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 23, 2003 AMEREN CORPORATION (Exact name of registrant as specified in its charter) Missouri 1-14756 43-1723446 (State or other jurisdiction (Commission (I.R.S. Employer of incorporation) File Number) Identification No.) 1901 Chouteau Avenue, St. Louis, Missouri 63103 (Address of principal executive offices and Zip Code) Registrant's telephone number, including area code: (314) 621-3222 ITEM 5. OTHER EVENTS AND REGULATION FD DISCLOSURE. On May 23, 2003, Union Electric Company, which operates as AmerenUE, a subsidiary of the Registrant, issued a press release announcing that it had filed a request with the Missouri Public Service Commission for a phased-in $26.7 million increase in natural gas delivery rates. The press release is attached as Exhibit 99.1 and is incorporated herein by reference. ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS. (c) Exhibits. 99.1 Press release, dated May 23, 2003, issued by Union Electric Company. SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. AMEREN CORPORATION (Registrant) By /s/ Martin J. Lyons ----------------------------------- Name: Martin J. Lyons Title: Vice President and Controller (Principal Accounting Officer) Date: May 23, 2003 2 Exhibit Index ------------- Exhibit No. Description ---------- ----------- 99.1 - Press release dated May 23, 2003, issued by Union Electric Company. 3