Exhibit 99.1





                                   CERTIFICATE
                                 furnished under
                 Section 906 of the Sarbanes-Oxley Act of 2002.

     I, Charles W. Mueller,  chief executive  officer of Union Electric Company,
hereby  certify that to the best of my  knowledge,  the  accompanying  Report of
Union  Electric  Company on Form 10-Q for the quarter ended March 31, 2003 fully
complies  with the  requirements  of  Section  13(a) or 15(d) of the  Securities
Exchange  Act of 1934 and  that  information  contained  in such  Report  fairly
presents,  in all material  respects,  the  financial  condition  and results of
operations of Union Electric Company.



                                            /s/ Charles W. Mueller
                                            ------------------------------------
                                            Charles W. Mueller
                                            Chairman and Chief Executive Officer
                                            (Principal Executive Officer)


Date:  May 14, 2003



A signed  original of this  written  statement  required by Section 906 has been
provided  to Union  Electric  Company  and will be  retained  by Union  Electric
Company and  furnished to the  Securities  and Exchange  Commission or its staff
upon request.