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 28, 2002 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 Reference is made to Note 2 (Federal - Midwest ISO and Alliance RTO) to the "Notes to Consolidated Financial Statements (unaudited)" in Ameren Corporation's Form 10-Q for the quarterly period ended March 31, 2002, for a discussion of the Federal Energy Regulatory Commission's (FERC) April 25, 2002 order requiring the Alliance companies, including our subsidiaries, Union Electric Company (AmerenUE) and Central Illinois Public Service Company (AmerenCIPS), to select the regional transmission organization (RTO) in which they will participate within thirty days of the order. On May 28, 2002, we filed with the FERC indicating that we would return to the Midwest Independent System Operator (MISO), although the exact nature of our participation (whether as an individual transmission owner or through an independent transmission company) is subject to further negotiations. Until the tariffs and other material terms of our participation in the MISO are finalized and approved by the FERC, we cannot predict the impact ongoing RTO developments will have on our future financial condition, results of operation or liquidity. Safe Harbor Statement Statements made in this report, which are not based on historical facts, are "forward-looking" and, accordingly, involve risks and uncertainties that could cause actual results to differ materially from those discussed. Although such "forward-looking" statements have been made in good faith and are based on reasonable assumptions, there is no assurance that the expected results will be achieved. These statements include (without limitation) statements as to future expectations, beliefs, plans, strategies, objectives, events, conditions and financial performance. In connection with the "Safe Harbor" provisions of the Private Securities Litigation Reform Act of 1995, we are providing this cautionary statement to identify important factors that could cause actual results to differ materially from those anticipated. The following factors could cause results to differ materially from management expectations as suggested by such "forward-looking" statements: o the effects of regulatory actions, including changes in regulatory policy; o the effects of participation in a FERC-approved RTO, including activities associated with the MISO and the Alliance RTO; and o legal and administrative proceedings. 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 ------------------------------ Martin J. Lyons Controller (Principal Accounting Officer) Date: May 30, 2002 2