Exhibit 31.1
                                                                   Page 1 of 2


                     RULE 13a-14(a)/15d-14(a) CERTIFICATION
                         OF PRINCIPAL EXECUTIVE OFFICER
           (required by Section 302 of the Sarbanes-Oxley Act of 2002)


     I, Charles W. Mueller, certify that:

     1.   I have  reviewed  this  report on Form 10-Q for the  quarterly  period
ended June 30, 2003 of Union Electric Company;

     2.   Based on my  knowledge,  this  report  does  not  contain  any  untrue
statement of a material fact or omit to state a material fact  necessary to make
the statements made, in light of the  circumstances  under which such statements
were made, not misleading with respect to the period covered by this report;

     3.   Based on my knowledge,  the financial statements,  and other financial
information included in this report, fairly present in all material respects the
financial  condition,  results of operations and cash flows of the registrant as
of, and for, the periods presented in this report;

     4.   The registrant's  other  certifying  officer and I are responsible for
establishing and maintaining  disclosure  controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

          a)   Designed such disclosure controls and procedures,  or caused such
               disclosure  controls  and  procedures  to be  designed  under our
               supervision,  to ensure that material information relating to the
               registrant,  including  its  consolidated  subsidiaries,  is made
               known to us by others within those entities,  particularly during
               the period in which this report is being prepared;

          b)   Evaluated  the  effectiveness  of  the  registrant's   disclosure
               controls  and   procedures  and  presented  in  this  report  our
               conclusions  about the  effectiveness of the disclosure  controls
               and  procedures,  as of the  end of the  period  covered  by this
               report based on such evaluation; and

          c)   Disclosed in this report any change in the registrant's  internal
               control  over  financial   reporting  that  occurred  during  the
               registrant's most recent fiscal quarter (the registrant's  fourth
               fiscal  quarter  in  the  case  of an  annual  report)  that  has
               materially  affected,  or  is  reasonably  likely  to  materially
               affect,   the   registrant's   internal  control  over  financial
               reporting; and

     5.   The registrant's other certifying officer and I have disclosed,  based
on our most recent evaluation of internal control over financial  reporting,  to
the  registrant's  auditors  and the audit  committee of  registrant's  board of
directors (or persons performing the equivalent functions):

          a)   All  significant  deficiencies  and  material  weaknesses  in the
               design or  operation  of internal  control  which are  reasonably
               likely to adversely  affect the  registrant's  ability to record,
               process, summarize and report financial information; and

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                                                                    Exhibit 31.1
                                                                    Page 2 of 2



          b)   Any fraud,  whether or not material,  that involves management or
               other employees who have a significant  role in the  registrant's
               internal control over financial reporting.



Date:  August 14, 2003



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