Exhibit 99.1

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

     I, Gary L. Rainwater,  chief executive  officer of Central  Illinois Public
Service  Company,  hereby  certify  that  to  the  best  of  my  knowledge,  the
accompanying  Report of Central Illinois Public Service 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 Central Illinois Public Service
Company.




                                            /s/ Gary L. Rainwater
                                           ------------------------------------
                                                    Gary L. Rainwater
                                          President 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 Central Illinois Public Service Company and will be retained by
Central  Illinois  Public  Service  Company and furnished to the  Securities and
Exchange Commission or its staff upon request.