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                                                                     Exhibit 4.2

                       [Union Electric Company Letterhead]

                                  COMPANY ORDER

                                                      March 10, 2003


The Bank of New York
101 Barclay Street
Floor 21W
New York, New York 10286

Ladies and Gentlemen:

       Application is hereby made to The Bank of New York, a New York banking
corporation, as trustee (the "Trustee"), under the Indenture dated as of August
15, 2002 (the "Indenture"), between Union Electric Company, a Missouri
corporation (the "Company"), and the Trustee for the authentication and delivery
of $184,000,000 aggregate principal amount of the Company's 5.50% Senior Secured
Notes due 2034 (the "Notes"), pursuant to the provisions of Article II of the
Indenture. On or after the Release Date, the Company, in its discretion, may
change the descriptive title of the Notes to delete the word "Secured" from such
descriptive title. All capitalized terms not defined herein which are defined in
the Indenture shall have the same meaning as used in the Indenture.

       In connection with this Company Order, there are delivered to you
herewith the following:

       1.     Certified copies of the resolutions adopted by the Board of
              Directors of the Company authorizing this Company Order and the
              issuance and sale of the Notes by the Company pursuant to Section
              2.05(c)(1) of the Indenture;

       2.     Opinions of Counsel addressed to you or in which it is stated that
              you may rely pursuant to Section 2.05(c)(2) of the Indenture;

       3.     Expert's certificate pursuant to Section 2.05(c)(3) of the
              Indenture;

       4.     Officers' Certificate pursuant to Section 2.05(c)(4) of the
              Indenture;

       5.     A Global Note representing the Notes and, pursuant to Section
              2.05(c) of the Indenture, specifying the terms of the Notes (which
              terms are incorporated by reference herein) executed on behalf of
              the Company in accordance with the terms of Section 2.05(a) of the
              Indenture; and

       6.     Pursuant to Section 2.05(c)(3) of the Indenture, the Company's
              First Mortgage Bonds designated "First Mortgage Bonds, Senior
              Notes Series BB" (the "First Mortgage Bonds") in the principal
              amount of $184,000,000 relating to the Notes, fully registered in
              the name of the Trustee in trust for the benefit of the Holders
              from time to time of such Notes.

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       You are hereby instructed to authenticate the Global Note representing
the Notes and deliver it to The Depository Trust Company ("DTC") or its
custodian. The Global Note representing the Notes is to be held for delivery to
BNY Capital Markets, Inc. and J.P. Morgan Securities Inc., on behalf of the
several underwriters, against payment therefor at the closing in respect of the
sale thereof, such closing to be held at 10:00 a.m., New York time, March 10,
2003, at the offices of Pillsbury Winthrop LLP, One Battery Park Plaza, New
York, NY 10004.

       Please acknowledge receipt of the Global Note representing the Notes, the
instructions referred to above and the supporting documentation pursuant to the
Indenture referred to above.

                                        Very truly yours,


                                        Union Electric Company
                                        (d/b/a AmerenUE)


                                        By: /s/ Jerre E. Birdsong
                                            -----------------------------------
                                            Name:  Jerre E. Birdsong
                                            Title: Vice President and Treasurer

       Receipt from the Company of the Global Note representing the Notes,
certain instructions related thereto and the supporting documentation pursuant
to the Indenture, including the First Mortgage Bonds in trust for the benefit of
the Holders in connection with the authentication and delivery of the Notes is
hereby acknowledged.

                                        The Bank of New York,
                                        as Trustee


                                        By: /s/ Belinda Brown
                                            -----------------------------------
                                            Name:  Belinda Brown
                                            Title: Vice President