Exhibit 99.1

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


     In connection with the accompanying Annual Report of the Ameren Corporation
Employee Long-Term Savings Plan - IUOE No. 148 (the "Plan") on Form 11-K for the
year  ended  December  31,  2002 as  filed  with  the  Securities  and  Exchange
Commission (the "Report"), I, Donna K. Martin, Vice President,  Human Resources,
of Ameren  Services  Company,  the  administrator  of the Plan,  hereby certify,
pursuant to 18 U.S.C.  Section 1350,  as adopted  pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(1)  The Report fully  complies with the  requirements  of 13(a) or 15(d) of the
     Securities Act of 1934; and

(2)  The information  contained in the Report fairly  presents,  in all material
     respects, the financial condition and results of operations of the Plan.

     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.



                                                /s/ Donna K. Martin
                                                -------------------------------
                                                Donna K. Martin
                                                Vice President, Human Resources
                                                Ameren Services Company
                                                (Plan Administrator)

Date:  June 30, 2003