Exhibit 4.2


WHEN RECORDED
MAIL TO:

Gerald L. Waters
Union Electric Company
1901 Chouteau Avenue
St. Louis, MO  61303
================================================================================



                       Executed in 35 Counterparts, No. 35



                             SUPPLEMENTAL INDENTURE

                             DATED FEBRUARY 1, 2004

                             UNION ELECTRIC COMPANY

                                       TO

                              THE BANK OF NEW YORK,
                                   AS TRUSTEE


                     --------------------------------------


             (SUPPLEMENTAL TO THE INDENTURE OF MORTGAGE AND DEED OF
               TRUST DATED JUNE 15, 1937, AS AMENDED, EXECUTED BY
                             UNION ELECTRIC COMPANY
                      TO THE BANK OF NEW YORK, AS TRUSTEE)

                     --------------------------------------


                 First Mortgage Bonds, Environmental Improvement
                           Series 2004B (1998B Bonds)


    This instrument was prepared by Steven R. Sullivan, Senior Vice President
 Governmental/Regulatory Policy, General Counsel and Secretary of Union Electric
    Company, 1901 Chouteau Avenue, St. Louis, Missouri 63103, (314) 554-2098.


<PAGE>


     SUPPLEMENTAL  INDENTURE,  dated the 1st day of  February,  Two thousand and
four (2004) made by and between UNION ELECTRIC COMPANY, a corporation  organized
and  existing  under the laws of the State of Missouri  (hereinafter  called the
"Company"), party of the first part, and The Bank of New York (successor trustee
to Bank of America,  National Association,  formerly Boatmen's Trust Company), a
bank existing  under the laws of the State of New York  (hereinafter  called the
"Trustee"),  as Trustee  under the Indenture of Mortgage and Deed of Trust dated
June 15, 1937, hereinafter mentioned, party of the second part:

     WHEREAS,  the Company has heretofore  executed and delivered to the Trustee
its Indenture of Mortgage and Deed of Trust, dated June 15, 1937, as amended May
1, 1941,  April 1, 1971,  February 1, 1974,  July 7, 1980,  February 1, 2000 and
August 15, 2002 (said  Indenture  of  Mortgage  and Deed of Trust as so amended,
being  hereinafter  referred  to as the  "Original  Indenture"),  to secure  the
payment of the principal of and the interest (and premium,  if any) on all bonds
at any time  issued and  outstanding  thereunder,  and  indentures  supplemental
thereto dated June 15, 1937, May 1, 1941,  March 17, 1942, April 13, 1945, April
27, 1945,  October 1, 1945, April 11, 1947, April 13, 1949,  September 13, 1950,
December 1, 1950,  September 20, 1951, May 1, 1952,  March 1, 1954, May 1, 1955,
August 31, 1955, April 1, 1956, July 1, 1956, August 1, 1957,  February 1, 1958,
March 1, 1958,  November 5, 1958,  March 16, 1959,  June 24, 1959,  December 11,
1959, August 17, 1960,  September 1, 1960, October 24, 1960, June 30, 1961, July
1, 1961, August 9, 1962,  September 30, 1963,  November 1, 1963, March 12, 1965,
April 1, 1965,  April 14, 1966, May 1, 1966,  February 17, 1967,  March 1, 1967,
February 19, 1968, March 15, 1968,  August 21, 1968, April 7, 1969, May 1, 1969,
September 12, 1969,  October 1, 1969,  March 26, 1970,  April 1, 1970,  June 12,
1970,  January 1, 1971,  April 1, 1971,  September  15, 1971,  December 3, 1973,
February 1, 1974,  April 25,  1974,  February 3, 1975,  March 1, 1975,  June 11,
1975, May 12, 1976, August 16, 1976, April 26, 1977, October 15, 1977,  November
7, 1977,  December 1, 1977, August 1, 1978, October 12, 1979,  November 1, 1979,
July 7, 1980,  August 1, 1980,  August 20,  1980,  February 1, 1981,  October 8,
1981, August 27, 1982, September 1, 1982, December 15, 1982, March 1, 1983, June
21, 1984,  December 12, 1984, June 11, 1985,  March 1, 1986, May 1, 1986, May 1,
1990, December 1, 1991,  December 4, 1991, January 1, 1992,  September 30, 1992,
October 1, 1992,  December 1, 1992,  February 1, 1993, February 18, 1993, May 1,
1993, August 1, 1993, October 1, 1993, January 1, 1994, February 1, 2000, August
15,  2002,  March 5, 2003,  April 1, 2003,  July 15,  2003 and  October 1, 2003,
respectively,  have  heretofore  been  entered  into between the Company and the
Trustee; and

     WHEREAS,  Bonds  have  heretofore  been  issued  by the  Company  under the
Original Indenture as follows:

          (1)  $80,000,000  principal  amount of First  Mortgage and  Collateral
     Trust Bonds,  3-3/4% Series due 1962, all of which have been redeemed prior
     to the date of the execution hereof;

          (2)  $90,000,000  principal  amount of First  Mortgage and  Collateral
     Trust  Bonds,   3-3/8%  Series  due  1971,   which  are  described  in  the
     Supplemental   Indenture  dated

<PAGE>

     May 1, 1941  (hereinafter  called  the  "Supplemental  Indenture  of May 1,
     1941"),  all of which have been paid at  maturity  prior to the date of the
     execution hereof;

          (3)  $13,000,000  principal  amount of First  Mortgage and  Collateral
     Trust  Bonds,  2-3/4%  Series  due 1975  (herein  called the "Bonds of 1975
     Series"),  which are described in the Supplemental  Indenture dated October
     1, 1945  (hereinafter  called  the  "Supplemental  Indenture  of October 1,
     1945"),  all of which have been paid at  maturity  prior to the date of the
     execution hereof;

          (4)  $25,000,000  principal  amount of First  Mortgage and  Collateral
     Trust  Bonds,  2-7/8%  Series  due 1980  (herein  called the "Bonds of 1980
     Series"),  which are described in the Supplemental Indenture dated December
     1, 1950  (hereinafter  called the  "Supplemental  Indenture  of December 1,
     1950"),  all of which have been paid at  maturity  prior to the date of the
     execution hereof;

          (5)  $30,000,000  principal  amount of First  Mortgage and  Collateral
     Trust  Bonds,  3-1/4%  Series  due 1982  (herein  called the "Bonds of 1982
     Series"),  which are described in the  Supplemental  Indenture dated May 1,
     1952 (hereinafter called the "Supplemental  Indenture of May 1, 1952"), all
     of which  have been  paid at  maturity  prior to the date of the  execution
     hereof;

          (6)  $40,000,000  principal  amount of First  Mortgage  Bonds,  3-3/4%
     Series  due 1986  (herein  called the  "Bonds of 1986  Series"),  which are
     described in the  Supplemental  Indenture  dated July 1, 1956  (hereinafter
     called the  "Supplemental  Indenture of July 1,  1956"),  all of which have
     been paid at maturity prior to the date of the execution hereof;

          (7)  $35,000,000  principal  amount of First  Mortgage  Bonds,  4-3/8%
     Series  due 1988  (herein  called the  "Bonds of 1988  Series"),  which are
     described in the  Supplemental  Indenture dated March 1, 1958  (hereinafter
     called the  "Supplemental  Indenture of March 1, 1958"),  all of which have
     been paid at maturity prior to the date of the execution hereof;

          (8)  $50,000,000  principal  amount of First  Mortgage  Bonds,  4-3/4%
     Series  due 1990  (herein  called the  "Bonds of 1990  Series"),  which are
     described  in  the   Supplemental   Indenture   dated   September  1,  1960
     (hereinafter called the "Supplemental Indenture of September 1, 1960"), all
     of which  have been  paid at  maturity  prior to the date of the  execution
     hereof;

          (9)  $30,000,000  principal  amount of First  Mortgage  Bonds,  4-3/4%
     Series  due 1991  (herein  called the  "Bonds of 1991  Series"),  which are
     described in the  Supplemental  Indenture  dated July 1, 1961  (hereinafter
     called the  "Supplemental  Indenture of July 1,  1961"),  all of which have
     been paid at maturity prior to the date of the execution hereof;

          (10)  $30,000,000  principal  amount of First Mortgage  Bonds,  4-1/2%
     Series  due 1993  (herein  called the  "Bonds of 1993  Series"),  which are
     described in the

                                      -2-

<PAGE>

     Supplemental  Indenture  dated  November  1, 1963  (hereinafter  called the
     "Supplemental  Indenture  of  November  1,  1963"),  all of which have been
     redeemed prior to the date of the execution hereof;

          (11)  $35,000,000  principal  amount of First Mortgage  Bonds,  4-1/2%
     Series  due 1995  (herein  called the  "Bonds of 1995  Series"),  which are
     described in the  Supplemental  Indenture dated April 1, 1965  (hereinafter
     called the  "Supplemental  Indenture of April 1, 1965"),  all of which have
     been paid at maturity prior to the date of the execution hereof;

          (12)  $30,000,000  principal  amount of First Mortgage  Bonds,  5-1/2%
     Series  due 1996  (herein  called the  "Bonds of 1996  Series"),  which are
     described  in the  Supplemental  Indenture  dated May 1, 1966  (hereinafter
     called the "Supplemental Indenture of May 1, 1966"), all of which have been
     paid at maturity prior to the date of the execution hereof;

          (13)  $40,000,000  principal  amount of First Mortgage  Bonds,  5-1/2%
     Series  due 1997  (herein  called the  "Bonds of 1997  Series"),  which are
     described in the  Supplemental  Indenture dated March 1, 1967  (hereinafter
     called the  "Supplemental  Indenture of March 1, 1967"),  all of which have
     been paid at maturity prior to the date of the execution hereof;

          (14)  $50,000,000  principal amount of First Mortgage Bonds, 7% Series
     due 1998 (herein called the "Bonds of 1998 Series"), which are described in
     the  Supplemental  Indenture dated March 15, 1968  (hereinafter  called the
     "Supplemental  Indenture  of  March  15,  1968"),  all of which  have  been
     redeemed prior to the date of the execution hereof;

          (15)  $35,000,000  principal  amount of First Mortgage  Bonds,  7-3/8%
     Series due 1999 (herein called the "Bonds of May 1999  Series"),  which are
     described  in the  Supplemental  Indenture  dated May 1, 1969  (hereinafter
     called the "Supplemental Indenture of May 1, 1969"), all of which have been
     redeemed prior to the date of the execution hereof;

          (16)  $40,000,000  principal  amount of First Mortgage  Bonds,  8-1/4%
     Series due 1999 (herein called the "Bonds of October 1999  Series"),  which
     are  described  in  the  Supplemental   Indenture  dated  October  1,  1969
     (hereinafter  called the "Supplemental  Indenture of October 1, 1969"), all
     of which have been redeemed prior to the date of the execution hereof;

          (17)  $100,000,000  principal  amount of First Mortgage  Bonds,  9.95%
     Series due 1999 (herein called the "Bonds of November 1999 Series"),  which
     are  described  in  the  Supplemental  Indenture  dated  November  1,  1979
     (hereinafter called the "Supplemental  Indenture of November 1, 1979"), all
     of which have been redeemed prior to the date of the execution hereof;

                                      -3-

<PAGE>

          (18)  $60,000,000  principal amount of First Mortgage Bonds, 9% Series
     due 2000 (herein called the "Bonds of 2000 Series"), which are described in
     the  Supplemental  Indenture  dated April 1, 1970  (hereinafter  called the
     "Supplemental Indenture of April 1, 1970"), all of which have been redeemed
     prior to the date of the execution hereof;

          (19)  $50,000,000  principal  amount of First Mortgage  Bonds,  7-7/8%
     Series due 2001 (herein called the "Bonds of January 2001  Series"),  which
     are  described  in  the  Supplemental   Indenture  dated  January  1,  1971
     (hereinafter  called the "Supplemental  Indenture of January 1, 1971"), all
     of which have been redeemed prior to the date of the execution hereof;

          (20)  $50,000,000  principal  amount of First  Mortgage  Bonds, 7 5/8%
     Series due 2001 (herein called the "Bonds of April 2001 Series"), which are
     described in the  Supplemental  Indenture dated April 1, 1971  (hereinafter
     called the  "Supplemental  Indenture of April 1, 1971"),  all of which have
     been redeemed prior to the date of the execution hereof;

          (21)  $60,000,000  principal  amount of First  Mortgage  Bonds, 8 1/8%
     Series due 2001 (herein called the "Bonds of October 2001  Series"),  which
     are  described  in the  Supplemental  Indenture  dated  September  15, 1971
     (hereinafter  called the  "Supplemental  Indenture of September 15, 1971"),
     all of which have been redeemed prior to the date of the execution hereof;

          (22)  $70,000,000  principal  amount of First Mortgage  Bonds,  8-3/8%
     Series  due 2004  (herein  called the  "Bonds of 2004  Series"),  which are
     described in the Supplemental Indenture dated February 1, 1974 (hereinafter
     called the "Supplemental Indenture of February 1, 1974"), all of which have
     been redeemed prior to the date of the execution hereof;

          (23)  $70,000,000  principal  amount of First Mortgage Bonds,  10-1/2%
     Series  due 2005  (herein  called the  "Bonds of 2005  Series"),  which are
     described in the  Supplemental  Indenture dated March 1, 1975  (hereinafter
     called the  "Supplemental  Indenture of March 1, 1975"),  all of which have
     been redeemed prior to the date of the execution hereof;

          (24)  $70,000,000  principal  amount of First Mortgage  Bonds,  8-7/8%
     Series  due 2006  (herein  called the  "Bonds of 2006  Series"),  which are
     described in the Supplemental  Indenture dated August 16, 1976 (hereinafter
     called the "Supplemental  Indenture of August 16, 1976"), all of which have
     been redeemed prior to the date of the execution hereof;

          (25)  $27,085,000  principal  amount of First  Mortgage  Bonds,  5.80%
     Environmental   Improvement   Series  1977,  which  are  described  in  the
     Supplemental  Indenture  dated  October  15, 1977  (hereinafter  called the
     "Supplemental  Indenture  of  October  15,  1977"),  all of which have been
     redeemed prior to the date of the execution hereof;

                                      -4-

<PAGE>
          (26)  $60,000,000  principal  amount of First  Mortgage  Bonds, 8 5/8%
     Series  due 2007  (herein  called the  "Bonds of 2007  Series"),  which are
     described in the Supplemental Indenture dated December 1, 1977 (hereinafter
     called the "Supplemental Indenture of December 1, 1977"), all of which have
     been redeemed prior to the date of the execution hereof;

          (27)  $55,000,000  principal  amount of First  Mortgage  Bonds,  9.35%
     Series  due 2008  (herein  called the  "Bonds of 2008  Series"),  which are
     described in the Supplemental  Indenture dated August 1, 1978  (hereinafter
     called the "Supplemental  Indenture of August 1, 1978"),  all of which have
     been redeemed prior to the date of the execution hereof;

          (28)   $60,000,000   principal   amount  of  First   Mortgage   Bonds,
     Environmental   Improvement   Series  1980,  which  are  described  in  the
     Supplemental  Indenture  dated  August  1,  1980  (hereinafter  called  the
     "Supplemental  Indenture  of  August  1,  1980"),  all of which  have  been
     redeemed prior to the date of the execution hereof;

          (29)  $150,000,000  principal amount of First Mortgage Bonds,  15-3/8%
     Series due 1991 (herein called the "Bonds of February 1991 Series"),  which
     are  described  in  the  Supplemental  Indenture  dated  February  1,  1981
     (hereinafter called the "Supplemental  Indenture of February 1, 1981"), all
     of which have been redeemed prior to the date of the execution hereof;

          (30) $125,000,000 principal amount of First Mortgage Bonds, 15% Series
     due 1992 (herein called the "Bonds of 1992 Series"), which are described in
     the Supplemental  Indenture dated September 1, 1982 (hereinafter called the
     "Supplemental  Indenture of  September  1,  1982"),  all of which have been
     redeemed prior to the date of the execution hereof;

          (31) $100,000,000 principal amount of First Mortgage Bonds, 13% Series
     due 2013 (herein called the "Bonds of 2013 Series"), which are described in
     the  Supplemental  Indenture  dated March 1, 1983  (hereinafter  called the
     "Supplemental Indenture of March 1, 1983"), all of which have been redeemed
     prior to the date of the execution hereof;

          (32)  $100,000,000  principal  amount of First Mortgage Bonds,  9-3/8%
     Series  due 2016  (herein  called the  "Bonds of 2016  Series"),  which are
     described in the  Supplemental  Indenture dated March 1, 1986  (hereinafter
     called the  "Supplemental  Indenture of March 1, 1986"),  all of which have
     been redeemed prior to the date of the execution hereof;

          (33)  $100,000,000  principal  amount of First Mortgage Bonds,  8-7/8%
     Series  due 1996  (herein  called the  "Bonds of 1996  Series"),  which are
     described  in the  Supplemental  Indenture  dated May 1, 1986  (hereinafter
     called the "Supplemental Indenture of May 1, 1986"), all of which have been
     redeemed prior to the date of the execution hereof;

                                      -5-

<PAGE>

          (34)   $60,000,000   principal   amount  of  First   Mortgage   Bonds,
     Environmental   Improvement  Series  1990A,  which  are  described  in  the
     Supplemental   Indenture  dated  May  1,  1990   (hereinafter   called  the
     "Supplemental  Indenture of May 1, 1990"),  all of which have been redeemed
     prior to the date of the execution hereof;

          (35)  $125,000,000  principal  amount of First Mortgage Bonds,  8-3/4%
     Series  due 2021  (herein  called the  "Bonds of 2021  Series"),  which are
     described in the Supplemental Indenture dated December 1, 1991 (hereinafter
     called the "Supplemental Indenture of December 1, 1991"), all of which have
     been redeemed prior to the date of the execution hereof;

          (36)  $75,000,000  principal  amount of First  Mortgage  Bonds,  8.33%
     Series  due 2002  (herein  called the  "Bonds of 2002  Series"),  which are
     described in the Supplemental Indenture dated December 4, 1991 (hereinafter
     called the "Supplemental Indenture of December 4, 1991"), all of which have
     been paid at maturity prior to the date of the execution hereof;

          (37)  $100,000,000  principal  amount of First Mortgage  Bonds,  7.65%
     Series  due 2003  (herein  called the  "Bonds of 2003  Series"),  which are
     described in the Supplemental  Indenture dated January 1, 1992 (hereinafter
     called the "Supplemental  Indenture of January 1, 1992"), all of which have
     been paid at maturity prior to the date of the execution hereof;

          (38) $204,000,000  aggregate principal amount of First Mortgage Bonds,
     consisting of $100,000,000  principal  amount of 6-3/4% Series due 1999 and
     $104,000,000  principal amount of 8-1/4% Series due 2022 (herein called the
     "Bonds of 1999 Series" and "Bonds of 2022 Series", respectively), which are
     described in the Supplemental  Indenture dated October 1, 1992 (hereinafter
     called the "Supplemental Indenture of October 1, 1992"), of which the Bonds
     of 1999 Series have been paid at  maturity  prior to the date of  execution
     hereof and the Bonds of 2022 Series have been redeemed prior to the date of
     the execution hereof;

          (39) $170,000,000  aggregate principal amount of First Mortgage Bonds,
     consisting of  $85,000,000  principal  amount of 7-3/8% Series due 2004 and
     $85,000,000  principal  amount of 8% Series  due 2022  (herein  called  the
     "Bonds of  December  2004  Series"  and "Bonds of  December  2022  Series",
     respectively,  which are  described  in the  Supplemental  Indenture  dated
     December  1, 1992,  (hereinafter  called  the  "Supplemental  Indenture  of
     December 1,  1992"),  of which the Bonds of December  2022 Series have been
     redeemed  prior  to the  date of the  execution  hereof  and the  Bonds  of
     December 2004 Series are outstanding at the date of the execution hereof;

          (40)  $188,000,000  principal  amount of First Mortgage Bonds,  6-7/8%
     Series due 2004 (herein  called the "Bonds of August 2004  Series"),  which
     are  described  in  the  Supplemental  Indenture  dated  February  1,  1993
     (hereinafter called the "Supplemental  Indenture of February 1, 1993"), all
     of which are outstanding at the date of the execution hereof;

                                      -6-

<PAGE>

          (41)  $148,000,000  principal  amount of First Mortgage Bonds,  6-3/4%
     Series due 2008 (herein called the "Bonds of May 2008  Series"),  which are
     described  in the  Supplemental  Indenture  dated May 1, 1993  (hereinafter
     called  the  "Supplemental  Indenture  of May 1,  1993"),  all of which are
     outstanding at the date of the execution hereof;

          (42)  $75,000,000  principal  amount of First  Mortgage  Bonds,  7.15%
     Series  due 2023  (herein  called the  "Bonds of 2023  Series"),  which are
     described in the Supplemental  Indenture dated August 1, 1993  (hereinafter
     called the "Supplemental  Indenture of August 1, 1993"),  all of which have
     been redeemed prior to the date of the execution hereof;

          (43)   $44,000,000   principal   amount  of  First   Mortgage   Bonds,
     Environmental  Improvement  Series 1993  (herein  called the "Bonds of 2028
     Series"),  which are described in the Supplemental  Indenture dated October
     1, 1993  (hereinafter  called  the  "Supplemental  Indenture  of October 1,
     1993"), all of which are outstanding at the date of the execution hereof;

          (44) $100,000,000  principal amount of First Mortgage Bonds, 7% Series
     due 2024 (herein called the "Bonds of 2024 Series"), which are described in
     the Supplemental  Indenture dated January 1, 1994  (hereinafter  called the
     "Supplemental  Indenture of January 1, 1994"), all of which are outstanding
     at the date of the execution hereof;

          (45)  $173,000,000  principal  amount of First Mortgage Bonds,  Senior
     Notes  Series AA  (herein  called the  "Bonds of 2012  Series"),  which are
     described in the Supplemental  Indenture dated August 15, 2002 (hereinafter
     called the "Supplemental  Indenture of August 15, 2002"),  all of which are
     outstanding at the date of the execution hereof;

          (46)  $184,000,000  principal  amount of First Mortgage Bonds,  Senior
     Notes  Series BB  (herein  called the  "Bonds of 2034  Series"),  which are
     described in the  Supplemental  Indenture dated March 5, 2003  (hereinafter
     called the  "Supplemental  Indenture of March 5,  2003"),  all of which are
     outstanding at the date of the execution hereof;

          (47)  $114,000,000  principal  amount of First Mortgage Bonds,  Senior
     Notes  Series CC  (herein  called the  "Bonds of 2015  Series"),  which are
     described in the  Supplemental  Indenture dated April 1, 2003  (hereinafter
     called the  "Supplemental  Indenture of April 1,  2003"),  all of which are
     outstanding at the date of the execution hereof;

          (48)  $200,000,000  principal  amount of First Mortgage Bonds,  Senior
     Notes  Series DD  (herein  called the  "Bonds of 2018  Series"),  which are
     described in the  Supplemental  Indenture dated July 15, 2003  (hereinafter
     called the  "Supplemental  Indenture of July 15,  2003"),  all of which are
     outstanding at the date of the execution hereof; and

                                      -7-

<PAGE>

          (49)  $200,000,000  principal  amount of First Mortgage Bonds,  Senior
     Notes  Series EE  (herein  called the  "Bonds of 2013  Series"),  which are
     described in the Supplemental  Indenture dated October 1, 2003 (hereinafter
     called the "Supplemental  Indenture of October 1, 2003"),  all of which are
     outstanding at the date of the execution hereof; and

     WHEREAS, the following Bonds will be issued by the Company pursuant to this
Supplemental  Indenture or pursuant to a separate  Supplemental  Indenture  each
dated  February 1, 2004 and each series of such Bonds will be  outstanding  upon
the authentication by the Trustee of such Bonds:

          (A)   $50,000,000   principal   amount   of  First   Mortgage   Bonds,
     Environmental  Improvement  Series 2004B (1998B Bonds)  (herein  called the
     "New  Bonds"),  which are  described in the  Supplemental  Indenture  dated
     February 1, 2004 (hereinafter  called "this Supplemental  Indenture" or the
     "Supplemental Indenture of February 1, 2004 (2004B)"), all of which will be
     outstanding upon the authentication by the Trustee of the New Bonds; and

          (B)   $60,000,000   principal   amount   of  First   Mortgage   Bonds,
     Environmental  Improvement  Series 2004A (1998A Bonds)  (herein  called the
     "Bonds of 2033 (Series  1998A)"),  which are described in the  Supplemental
     Indenture  dated  February 1, 2004  (hereinafter  called the  "Supplemental
     Indenture of February 1, 2004  (2004A)"),  all of which will be outstanding
     upon the authentication by the Trustee of the Bonds of 2033 (Series 1998A);

          (C)   $50,000,000   principal   amount   of  First   Mortgage   Bonds,
     Environmental  Improvement  Series 2004C (1998C Bonds)  (herein  called the
     "Bonds of 2033 (Series  1998C)"),  which are described in the  Supplemental
     Indenture  dated  February 1, 2004  (hereinafter  called the  "Supplemental
     Indenture of February 1, 2004  (2004C)"),  all of which will be outstanding
     upon the authentication by the Trustee of the Bonds of 2033 (Series 1998C);

     and

     WHEREAS,  the Company on August 31, 1955 acquired all of the  properties of
Union  Electric  Power  Company,  the  Subsidiary as defined in Article I of the
Original  Indenture,  upon the  dissolution of the Subsidiary;  the Company,  by
Supplemental  Indenture dated August 31, 1955, conveyed all of the properties so
acquired (other than property of the character  defined as excepted  property in
the granting  clauses of the Original  Indenture)  to the Trustee upon the terms
and trusts in the Original Indenture and the indentures supplemental thereto set
forth for the equal and  proportionate  benefit and  security of all present and
future holders of the Bonds and coupons issued and to be issued thereunder,  all
the  shares  of  stock  of the  Subsidiary  were  released  from the lien of the
Original  Indenture;  and the  Company  became  entitled  to change the  general
designation of the Bonds so as to omit the words "and Collateral Trust"; and

                                      -8-

<PAGE>

     WHEREAS,  the Articles of Incorporation of the Company were duly amended on
April 23, 1956, to change its  corporate  name from "Union  Electric  Company of
Missouri" to "Union Electric Company"; and

     WHEREAS,  the  Articles  of  Agreement  of the  Trustee  were duly  amended
effective on January 4, 1982 to change its corporate  name from "St. Louis Union
Trust Company" to "Centerre Trust Company of St. Louis",  and further amended on
December 9, 1988, to change its corporate name from  "Centerre  Trust Company of
St. Louis" to "Boatmen's Trust Company"; and

     WHEREAS,  that on March 13,  1998,  Boatmen's  Trust  Company  merged  into
NationsBank,  National  Association and effective July 5, 1999, changed its name
to Bank of America, National Association; and

     WHEREAS,  that on February 1, 2000,  The Bank of New York, as transferee of
the corporate trust business of Bank of America,  National Association (formerly
known as Boatmen's Trust Company), Trustee under the Original Indenture,  became
successor Trustee under the Original Indenture; and

     WHEREAS,  the Company is entitled  at this time to have  authenticated  and
delivered  additional  Bonds on the basis of property  additions upon compliance
with and pursuant to the  provisions  of Article III,  Section 4 of the Original
Indenture; and

     WHEREAS,  the  Company  has  entered  into a  Loan  Agreement  dated  as of
September 1, 1998 (the "Original Loan Agreement")  with the State  Environmental
Improvement  and  Energy  Resources  Authority  of the  State of  Missouri  (the
"Authority")  pursuant  to which  the  Authority  agreed  to  issue  $50,000,000
aggregate  principal amount of its Environmental  Improvement  Revenue Refunding
Bonds (Union Electric Company Project) Series 1998B (the "Authority Bonds"), all
of which are presently outstanding and loan the proceeds thereof to the Company;
and

     WHEREAS,  the Authority Bonds were issued pursuant to an Indenture of Trust
dated as of September 1, 1998 (the "Original  Authority Bond Indenture") between
the Authority and UMB Bank & Trust,  N.A., as successor to State Street Bank and
Trust Company of Missouri, N.A., as trustee (the "Authority Bond Trustee"); and

     WHEREAS,  the Company has  determined  it to be necessary  and desirable to
further  secure  rights of the owners of the  Authority  Bonds to the payment of
principal and interest on the Authority Bonds by obtaining a Financial  Guaranty
Insurance  Policy  with  respect to the  Authority  Bonds (the  "Authority  Bond
Insurance  Policy") from MBIA Insurance  Corporation and in furtherance  thereof
(i) the Authority and the Authority  Bond Trustee will enter into an Amended and
Restated  Indenture of Trust dated as of February 1, 2004 (the  "Authority  Bond
Indenture") which amends and restates the Original Authority Bond Indenture, and
(ii) the Authority  and the Company will enter into the First  Amendment to Loan
Agreement  dated  as  of  February  1,  2004  (the  "First   Amendment  to  Loan
Agreement"),  which  amends the  Original  Loan

                                      -9-

<PAGE>

Agreement  (the Original  Loan  Agreement as so amended is referred to herein as
the "Agreement"); and

     WHEREAS,  in connection with obtaining the Authority Bond Insurance Policy,
the Company desires by this  Supplemental  Indenture to provide for the issuance
to the  Authority  Bond  Trustee  of a new  series of Bonds  under the  Original
Indenture as security for the Company's  obligations  under the  Agreement  with
respect to the payment of the Authority Bonds, to have the designation  provided
in Article I, Section 1 hereof (herein called the "New Bonds"), and the Original
Indenture provides that certain terms and provisions, as determined by the Board
of  Directors  of the  Company,  of the Bonds of any  particular  series  may be
expressed  in and  provided  by the  execution  of an  appropriate  supplemental
indenture; and

     WHEREAS,  the Original  Indenture provides that the Company and the Trustee
may enter into indentures supplemental to the Original Indenture specifically to
convey,  transfer  and assign to the  Trustee  and to subject to the lien of the
Original Indenture additional properties acquired by the Company; and

     WHEREAS, the Company, in the exercise of the powers and authority conferred
upon and  reserved to it under the  provisions  of the  Original  Indenture  and
pursuant to appropriate resolutions of the Board of Directors, has duly resolved
and  determined  to make,  execute  and  deliver to the  Trustee a  Supplemental
Indenture in the form hereof for the purposes herein provided; and

     WHEREAS,   all   conditions  and   requirements   necessary  to  make  this
Supplemental  Indenture a valid,  binding and legal  instrument  have been done,
performed and  fulfilled and the execution and delivery  hereof have been in all
respects duly authorized;

     NOW, THEREFORE, THIS INDENTURE WITNESSETH:

     That, in  consideration  of the premises and of the mutual covenants herein
contained  and of the  acceptance of this trust by the Trustee and of the sum of
One Dollar  duly paid by the Trustee to the Company at or before the time of the
execution of this Supplemental Indenture,  and of other valuable considerations,
the receipt whereof is hereby  acknowledged,  and in order further to secure the
payment of the principal of and interest  (and premium,  if any) on all Bonds at
any time issued and outstanding under the Original Indenture, according to their
tenor and effect,  and to secure the Company's  obligations  under the Agreement
with respect to the payment of the Authority Bonds, the Company has executed and
delivered  this  Supplemental  Indenture  and  has  granted,   bargained,  sold,
warranted,   aliened,  remised,  released,  conveyed,   assigned,   transferred,
mortgaged,  pledged,  set over and confirmed  and by these  presents does grant,
bargain,  sell, warrant,  alien,  remise,  release,  convey,  assign,  transfer,
mortgage,  pledge,  set over and confirm unto The Bank of New York,  as Trustee,
and to its  successors in trust under the Original  Indenture  forever,  all and
singular the following described properties (in addition to all other properties
heretofore  subjected to the lien of the Original  Indenture and not  heretofore
released from the lien thereof) - that is to say:

                                      -10-

<PAGE>

                                      FIRST

     ALL power houses, plants, buildings and other structures,  dams, dam sites,
substations, heating plants, gas works, holders and tanks, together with all and
singular  the  electric,  heating,  gas and  mechanical  appliances  appurtenant
thereto of every nature whatsoever,  now owned by the Company, including all and
singular  the  machinery,  engines,  boilers,  furnaces,  generators,   dynamos,
turbines and motors,  and all and every  character of  mechanical  appliance for
generating or producing  electricity,  steam,  gas and other agencies for light,
heat,  cold, or power or other purposes,  and all  transmission and distribution
systems used for the transmission  and  distribution of electricity,  steam, gas
and  other  agencies  for  light,  heat,  cold or  power  or any  other  purpose
whatsoever,  whether underground or overhead, surface or otherwise, now owned by
the Company,  including  all poles,  towers,  posts,  wires,  cables,  conduits,
manholes,  mains, pipes, tubes, drains,  furnaces,  switchboards,  transformers,
conductors,   insulators,   supports,  meters,  lamps,  fuses,  junction  boxes,
regulator  stations,  and other electric,  steam and gas fixtures and apparatus;
all of the  aforementioned  property being located in the City of St. Louis, the
counties  of  Adair,  Audrain,  Benton,  Bollinger,   Boone,  Butler,  Caldwell,
Callaway, Camden, Cape Girardeau,  Clark, Clay, Clinton, Cole, Cooper, Crawford,
Daviess, Dunklin,  Franklin,  Gasconade,  Howard, Iron, Jefferson,  Knox, Lewis,
Lincoln,  Livingston,  Macon,  Madison,  Maries,  Marion,  Miller,  Mississippi,
Moniteau,  Montgomery,  Morgan,  New Madrid,  Osage,  Pemiscot,  Perry,  Pettis,
Phelps, Pike, Pulaski, Ralls, Randolph, Ray, Reynolds,  Ripley, St. Charles, St.
Francois, Ste. Genevieve, St. Louis, Saline, Schuyler, Scott, Stoddard,  Warren,
Washington,  and Wayne,  Missouri,  the counties of Adams,  Alexander,  Calhoun,
Franklin,  Hancock,  Henderson,  Jackson,  Jersey,  Macoupin,  Madison,  Massac,
Monroe,  Perry, Pike, Pulaski, St. Clair, Union, and Washington,  Illinois,  and
the counties of Des Moines, Henry, Johnson, Lee, and Washington, Iowa, upon real
estate owned by the Company, or occupied by it under rights to so occupy,  which
real estate is  described  in the  Indenture of Mortgage and Deed of Trust dated
June 15, 1937, in the Supplemental Indentures dated May 1, 1941, March 17, 1942,
April 13, 1945, April 27, 1945, October 1, 1945, April 11, 1947, April 13, 1949,
September 13, 1950, December 1, 1950,  September 20, 1951, May 1, 1952, March 1,
1954, May 1, 1955, August 31, 1955, April 1, 1956, July 1, 1956, August 1, 1957,
February 1, 1958,  March 1, 1958,  November 5, 1958,  March 16,  1959,  June 24,
1959,  December 11, 1959, August 17, 1960,  September 1, 1960, October 24, 1960,
June 30, 1961,  July 1, 1961,  August 9, 1962,  September 30, 1963,  November 1,
1963, March 12, 1965,  April 1, 1965, April 14, 1966, May 1, 1966,  February 17,
1967, March 1, 1967,  February 19, 1968, March 15, 1968,  August 21, 1968, April
7, 1969, May 1, 1969, September 12, 1969, October 1, 1969, March 26, 1970, April
1, 1970,  June 12, 1970,  January 1, 1971,  April 1, 1971,  September  15, 1971,
December 3, 1973,  February 1, 1974, April 25, 1974,  February 3, 1975, March 1,
1975, June 11, 1975, May 12, 1976, August 16, 1976, April 26, 1977,  October 15,
1977,  November 7, 1977,  December 1, 1977,  August 1, 1978,  October 12,  1979,
November 1, 1979,  July 7, 1980,  August 1, 1980,  August 20, 1980,  February 1,
1981,  October 8, 1981, August 27, 1982,  September 1, 1982,  December 15, 1982,
March 1, 1983, June 21, 1984,  December 12, 1984, June 11, 1985,  March 1, 1986,
May 1, 1986, May 1, 1990,  December 1, 1991,  December 4, 1991, January 1, 1992,
September  30,  1992,  October 1, 1992,  December  1,  1992,  February  1, 1993,
February  18, 1993,  May 1, 1993,  August 1, 1993,  October 1, 1993,  January 1,
1994,  February 1, 2000, August 15, 2002, March 5, 2003, April 1, 2003, July 15,
2003,  October 1, 2003 and in this  Supplemental  Indenture  and the seven other
Supplemental Indentures each dated

                                      -11-

<PAGE>

February  1,  2004,  or  attached  to or  connected  with  such  real  estate or
transmission  or  distribution  systems of the Company leading from or into such
real estate.


                                     SECOND

     ALSO,  (except  as  in  the  Original  Indenture  expressly  excepted)  all
franchises and all permits, ordinances,  easements,  privileges,  immunities and
licenses,  all rights to construct,  maintain and operate overhead,  surface and
underground systems for the distribution and transmission of electricity, steam,
gas or other agencies for the supply to itself or others of light, heat, cold or
power, all  rights-of-way,  all waters,  water rights and flowage rights and all
grants and consents,  now owned or,  subject to the provisions of Article XII of
the Original Indenture, which it may hereafter acquire.

     ALSO,  (except  as  in  the  Original  Indenture  expressly  excepted)  all
inventions,  patent  rights and  licenses of every kind now owned by the Company
or, subject to the provisions of Article XII of the Original Indenture, which it
may hereafter acquire.


                                      THIRD

     ALSO,  subject to the provisions of Article XII of the Original  Indenture,
all other  property,  real,  personal  and mixed  (except  as  therein or herein
expressly  excepted)  of every nature and kind and  wheresoever  situated now or
hereafter  possessed by or  belonging to the Company,  or to which it is now, or
may at any time hereafter be, in any manner entitled at law or in equity.

     TO HAVE  AND TO  HOLD  all  said  properties,  real,  personal  and  mixed,
mortgaged,  pledged and conveyed by the Company as aforesaid,  or intended so to
be, unto the Trustee and its successors and assigns forever;

     SUBJECT,   HOWEVER,   to  the  exceptions  and   reservations  and  matters
hereinabove  recited,  to existing leases,  to existing liens upon rights of way
for transmission or distribution  line purposes,  as defined in Article I of the
Original  Indenture,  and  any  extensions  thereof,  and  subject  to  existing
easements for streets,  alleys,  highways,  rights-of-way  and railroad purposes
over,  upon and  across  certain of the  property  hereinbefore  described,  and
subject also to all the terms, conditions, agreements, covenants, exceptions and
reservations   expressed   or  provided  in  the  deeds  or  other   instruments
respectively  under and by virtue of which the Company  acquired the  properties
hereinabove described, and to undetermined liens and charges, if any, incidental
to construction or other existing permitted liens as defined in Article I of the
Original Indenture;

     IN TRUST, NEVERTHELESS, upon the terms and trusts in the Original Indenture
and the indentures supplemental thereto,  including this Supplemental Indenture,
set forth, for the equal and  proportionate  benefit and security of all present
and future holders of the Bonds and coupons issued and to be issued  thereunder,
or any of them,  without  preference  of any of said  Bonds and  coupons  of any
particular  series over the Bonds and coupons of any other series,  by reason of
priority in the time of the issue, sale or negotiation  thereof, or by reason of
the purpose of issue

                                      -12-

or otherwise howsoever,  except as otherwise provided in Section 2 of Article IV
of the Original Indenture.

     AND IT IS HEREBY  COVENANTED,  DECLARED  AND  AGREED,  by and  between  the
parties  hereto,  for the benefit of those who shall hold the Bonds and coupons,
or any of them to be issued under the Original Indenture, as follows:


                                    ARTICLE I

                          DESCRIPTION OF THE NEW BONDS

     Section 1.1.  There is hereby created a new series of Bonds to be executed,
authenticated  and delivered  under and secured by the Original  Indenture which
shall,  subject to the  provisions  of  Section 1 of Article II of the  Original
Indenture,  be designated as "First  Mortgage Bonds,  Environmental  Improvement
Series  2004B (1998B  Bonds)"  (the "New  Bonds") of the Company.  The New Bonds
shall be executed, authenticated and delivered in accordance with the provisions
of, and shall in all  respects  be subject to all of the terms,  conditions  and
covenants of, the Original  Indenture and shall be issued to, and  registered in
the name of, the Authority  Bond Trustee under the Authority  Bond  Indenture to
secure any and all  obligations  of the Company under the Agreement with respect
to the payment of the Authority Bonds.

     The New Bonds shall mature,  subject to prior  redemption,  on September 1,
2033,  and shall  bear  interest  at the same rate or rates of  interest  as the
Authority Bonds which, in turn,  shall be determined by the methods set forth in
the Authority Bond Indenture,  which provides for an Auction Rate, a Daily Rate,
a Weekly  Rate, a Commercial  Paper Rate or a Long-Term  Interest  Rate (each as
defined in the Authority Bonds  Indenture).  Reference is made to the provisions
of the Authority  Bond  Indenture  concerning the methods by which such interest
rates are  determined,  and the means by which the  method of  determining  such
interest  rates  may be  changed,  and  such  provisions  are  included  in this
Supplemental  Indenture as if fully set forth herein.  Interest on the New Bonds
is payable on the same dates as interest on the Authority  Bonds is paid,  until
the  principal  sum of the New  Bonds is paid in full.  The New  Bonds  shall be
payable as to  principal  and  interest  in any coin or  currency  of the United
States of America  which at the time of  payment is legal  tender for public and
private debts,  and shall be payable,  in immediately  available  funds,  at the
office of the Authority Bond Trustee.

     Section 1.2. The New Bonds shall not be assignable or  transferable  except
as permitted or required by Section 12.13 of the Authority Bond  Indenture.  Any
such transfer shall be effected at the principal  office or place of business of
the Trustee under the Original Indenture. The New Bonds are exchangeable for the
New Bonds of other denominations,  as in the Original Indenture provided, except
that payment of a service charge therefor will not be required by the Company.

     Notwithstanding  the  provisions of Section 6 of Article II of the Original
Indenture,  the New Bonds shall be dated their date of authentication  and shall
bear interest from the interest  payment date to which interest on the New Bonds
has been paid next  preceding the date thereof,

                                      -13-

<PAGE>

unless such date is an interest payment date to which interest has been paid, in
which case they shall bear interest from the date thereof.

     Upon any payment of the principal of and interest on, all or any portion of
the Authority Bonds,  whether at maturity or otherwise or upon provision for the
payment  thereof  having  been  made  in  accordance  with  Section  7.01 of the
Authority  Bond  Indenture,  the New Bonds in a  principal  amount  equal to the
principal amount of such Authority Bonds shall, to the extent of such payment of
principal  and  interest,  be  deemed  paid and the  obligation  of the  Company
thereunder  to make such payment  shall be discharged to such extent and, in the
case of the payment of  principal,  such New Bonds shall be  surrendered  to the
Company for cancellation as provided in and subject to the terms of Section 7.04
of the  Authority  Bond  Indenture.  The  Trustee  may at any time and all times
conclusively  assume that the  obligation  of the Company under the Agreement to
make  payments  with respect to the  principal of and interest on the  Authority
Bonds,  so far as such  payments  at the time have  become  due,  has been fully
satisfied and discharged pursuant to the foregoing sentence unless and until the
Trustee  shall have received a written  notice from the  Authority  Bond Trustee
signed by one of its  officers  stating (i) the timely  payment of  principal or
interest on, the Authority  Bonds has not been made, (ii) that the Company is in
arrears  as to the  payments  required  to be made by it to the  Authority  Bond
Trustee pursuant to the Agreement, and (iii) the amount of the arrearage.

     Section 1.3. The New Bonds and the Trustee's  certificate  on the New Bonds
shall be substantially in the following forms respectively:

                                      -14-

<PAGE>




                           [Form of Face of New Bond]

No. ____                                                         $________

                               Ill. C. C. No. 6315


 NOTWITHSTANDING ANY PROVISIONS HEREOF OR IN THE ORIGINAL INDENTURE THIS BOND IS
        NOT ASSIGNABLE OR TRANSFERABLE EXCEPT AS PERMITTED OR REQUIRED BY
    SECTION 12.13 OF THE AMENDED AND RESTATED INDENTURE OF TRUST DATED AS OF
    FEBRUARY 1, 2004, BETWEEN THE STATE ENVIRONMENTAL IMPROVEMENT AND ENERGY
   RESOURCES AUTHORITY OF THE STATE OF MISSOURI AND UMB BANK & TRUST, N.A., AS
 SUCCESSOR TO STATE STREET BANK AND TRUST COMPANY OF MISSOURI, N.A., AS TRUSTEE


                             UNION ELECTRIC COMPANY
             (Incorporated under the laws of the State of Missouri)
   First Mortgage Bonds, Environmental Improvement Series 2004B (1998B Bonds)

              Illinois Commerce Commission Identification No. 6315

     UNION ELECTRIC COMPANY, a corporation organized and existing under the laws
of the State of Missouri  (hereinafter  called the  "Company,"  which term shall
include any successor  corporation as defined in the Amended Indenture  referred
to on the reverse  hereof),  for value  received,  hereby promises to pay to UMB
Bank & Trust,  N.A.,  as  successor  to State  Street Bank and Trust  Company of
Missouri,  N.A.,  as trustee  under the  Authority  Bond  Indenture  hereinafter
referred  to,  or  registered  assigns,  the  sum  of  _________________________
Dollars, on the 1st day of September,  2033, subject to prior redemption, in any
coin or currency of the United States of America which at the time of payment is
legal tender for public and private debts, and to pay interest thereon,  in like
coin or currency,  at the same rate or rates of interest as the Authority  Bonds
(as  determined in  accordance  with the Authority  Bond  Indenture  referred to
below),  but in no event  shall the  interest  rate on this Bond  exceed  twelve
percent (12%) per annum.  Interest on overdue principal premium, if any, and, to
the  extent  permitted  by law,  on  overdue  interest,  shall be payable at the
interest rate payable on the Authority  Bonds.  Interest on this Bond is payable
on the same dates as interest on the Authority  Bonds, or, if this Bond shall be
duly called for redemption,  until the redemption  date, or if the Company shall
default in the payment of the principal hereof,  until the Company's  obligation
to pay principal  shall be  discharged  as provided in the Amended  Indenture is
paid,  until the principal  sum is paid in full.  The principal of, and interest
on, this Bond are payable, in immediately  available funds, at the office of the
Authority Bond Trustee hereinafter referred to.

     Under an Indenture  of Trust dated as of September 1, 1998,  as amended and
restated by the Amended and Restated  Indenture of Trust dated as of February 1,
2004 (as so amended and restated,  the "Authority Bond  Indenture")  between the
State  Environmental  Improvement and Energy Resources Authority of the State of
Missouri  (the  "Authority")  and UMB Bank & Trust,  N.A., as successor to State
Street Bank and Trust Company of Missouri, N.A., as trustee (the "Authority Bond
Trustee"), the Authority has issued its Environmental Improvement Revenue

                                      -15-

<PAGE>

Refunding Bonds (Union Electric  Company  Project) Series 1998B in the aggregate
principal amount of $50,000,000 (the "Authority Bonds").  The Company has agreed
to pay the principal of and interest on the Authority  Bonds  pursuant to a Loan
Agreement  dated as of September  1, 1998,  as  supplemented  and amended by the
First  Amendment to Loan Agreement  dated as of February 1, 2004 (as so amended,
the "Agreement") between the Company and the Authority. Pursuant to the Granting
Clause of the  Authority  Bond  Indenture,  this Bond is issued to the Authority
Bond  Trustee  to  secure  any and all  obligations  of the  Company  under  the
Agreement with respect to payment of the Authority  Bonds.  Payment of principal
of, or interest on, the Authority Bonds shall  constitute  payments on this Bond
as further provided herein and in the  Supplemental  Indenture dated February 1,
2004 pursuant to which this Bond has been issued (the "Supplemental Indenture").

     Upon any payment of the  principal  of, and interest on, all or any portion
of the Authority  Bonds,  whether at maturity or otherwise or upon provision for
the payment  thereof  having been made in  accordance  with  Section 7.01 of the
Authority Bond Indenture, a principal amount of this Bond equal to the principal
amount of such Authority Bonds shall, to the extent of such payment of principal
and interest,  be deemed paid and the  obligation  of the Company  thereunder to
make such  payment  shall be  discharged  to such extent and, in the case of the
payment of  principal,  such  Bonds  shall be  surrendered  to the  Company  for
cancellation  as provided in Section 7.04 of the Authority Bond  Indenture.  The
Trustee  (as  hereinafter  defined)  may at any time and all times  conclusively
assume that the  obligation of the Company to make payments  under the Agreement
with respect to the principal of, and interest on, the Authority  Bonds,  so far
as such  payments  at the time have  become due,  has been fully  satisfied  and
discharged pursuant to the foregoing sentence unless and until the Trustee shall
have received a written  notice from the Authority Bond Trustee signed by one of
its officers  stating (i) that timely  payment of principal  of, or interest on,
the Authority Bonds has not been made, (ii) that the Company is in arrears as to
the payments required to be made by it to the Authority Bond Trustee pursuant to
the Agreement, and (iii) the amount of the arrearage.

     This Bond shall not be entitled to any benefit under the Amended  Indenture
or any indenture  supplemental  thereto,  or become valid or obligatory  for any
purpose, until The Bank of New York, the Trustee under the Amended Indenture, or
a successor trustee thereto under the Amended  Indenture,  or an agent therefor,
shall have signed the form of certificate endorsed hereon.

     The  provisions of this Bond are  continued on the reverse  hereof and such
continued provisions shall for all purposes have the same effect as though fully
set forth at this place.

     IN WITNESS  WHEREOF,  Union  Electric  Company  has caused  this Bond to be
signed in its name by its Chairman of the Board or President or a Vice President
by  manual  signature  or a  facsimile  thereof,  and its  corporate  seal (or a
facsimile  thereof) to be hereto  affixed and  attested by its  Secretary  or an
Assistant Secretary by manual signature or a facsimile thereof.

                                      -16-

<PAGE>

         Dated,
                                       UNION ELECTRIC COMPANY,


                                       By
                                         ---------------------------------------
                                         Vice President
[CORPORATE SEAL]

Attest:


------------------------------
Secretary


                         [FORM OF TRUSTEE'S CERTIFICATE]

     This Bond is one of the Bonds, of the series designated therein,  described
in the within-mentioned Amended Indenture and Supplemental Indenture of February
1, 2004.

                                       THE BANK OF NEW YORK, as Trustee


                                       By
                                         ---------------------------------------
                                         Authorized Officer


                          [FORM OF REVERSE OF NEW BOND]

     This Bond is one of a duly authorized issue of Bonds of the Company (herein
called the "Bonds"), limited to an aggregate principal amount of $50,000,000, of
the series  hereinafter  specified,  all issued under and equally secured by the
Indenture  of Mortgage and Deed of Trust,  dated June 15, 1937,  executed by the
Company to The Bank of New York (successor trustee to Bank of America,  National
Association,  formerly  Boatmen's Trust Company),  as trustee (herein called the
"Trustee"),  as amended by  indentures  supplemental  thereto dated May 1, 1941,
April 1, 1971,  February 1, 1974, July 7, 1980,  February 1, 2000 and August 15,
2002,  between the Company and the Trustee (said mortgage and deed of trust,  as
so amended,  being herein  called the  "Amended  Indenture"),  to which  Amended
Indenture and all indentures supplemental thereto reference is hereby made for a
description  of the properties  mortgaged and pledged,  the nature and extent of
the security, the rights of the bearers or registered owners of the Bonds and of
the  Trustee in respect  thereto,  and the terms and  conditions  upon which the
Bonds are, and are to be, secured.  To the extent  permitted by, and as provided
in,  the  Amended  Indenture,   modifications  or  alterations  of  the  Amended
Indenture,  or of any  indenture  supplemental  thereto,  and of the  rights and
obligations  of the Company and of the holders of the Bonds may be made with the
consent of the Company by an affirmative  vote of not less than 60% in amount of
the Bonds entitled to vote then outstanding,  at a meeting of Bondholders called
and held as provided in the Amended Indenture, and by an affirmative vote of not
less  than 60% in  amount  of the

                                      -17-

<PAGE>

Bonds of any series  entitled  to vote then  outstanding  and  affected  by such
modification or alteration,  in case one or more but less than all of the series
of  Bonds  then  outstanding  under  the  Amended  Indenture  are  so  affected.
Additionally,  the Company may amend the Amended Indenture, as supplemented,  by
an  appropriate  written  consent  of not less than 60% in  aggregate  principal
amount of the Bonds  outstanding  (and,  if the rights of one or more,  but less
than all,  series of Bonds then  outstanding  are to be affected by action taken
pursuant to such consent, then also by consent of the holders of at least 60% in
principal  amount of each  series  of Bonds so to be  affected  and  outstanding
hereunder)  without a  meeting  of such  Bondholders.  No such  modification  or
alteration shall be made which will affect the terms of payment of the principal
of, or interest on, this Bond, which are unconditional.  The Bonds may be issued
in series,  for various  principal sums, may mature at different times, may bear
interest at different  rates and may otherwise vary as in the Amended  Indenture
provided.  This Bond is one of a series designated as the "First Mortgage Bonds,
Environmental  Improvement Series 2004B (1998B Bonds)" (herein called the "Bonds
of this  Series")  of the  Company,  issued  under and  secured  by the  Amended
Indenture and described in the indenture  (hereinafter  called the "Supplemental
Indenture")  dated  February  1, 2004,  between  the  Company  and the  Trustee,
supplemental to the Amended Indenture.

     The  Bonds  of  this  Series  are  not  entitled  to  the  benefit  of  any
improvement, maintenance or analogous fund.

     This Bond is, subject to the provisions of the Amended  Indenture,  subject
to  redemption  in the  amounts,  at the  times,  at the  prices  and  under the
circumstances  under which the Authority  Bonds are subject to redemption  under
the same terms and  circumstances  set forth in the Authority Bond Indenture for
the redemption of the Authority Bonds.

     This Bond is also subject to mandatory  redemption at the principal  amount
hereof plus accrued  interest to the date fixed for redemption if the Trustee or
the Company is  notified  that an "Event of Default"  under the  Authority  Bond
Indenture  has occurred and is  continuing  and the  Authority  Bond Trustee has
declared the principal  amount of all Authority  Bonds then  outstanding due and
payable in accordance with the Authority Bond Indenture.

     The  Company  may,  by notice to the  Trustee at least 60 days prior to any
date on which any  principal  amount  is due on this  Bond,  elect to  receive a
credit in respect of such  principal  payment  (a) for any Bonds of this  Series
then due which  have  been  redeemed  prior to such  principal  payment  date or
otherwise acquired and delivered to the Trustee for cancellation by said Trustee
prior to the giving of such notice,  or (b) for any  Authority  Bonds which have
been purchased, delivered for cancellation or previously redeemed, which in each
case have not  theretofore  been  applied  as a credit  against  such  principal
payment.  Each Bond with respect to which the Company elects to receive a credit
will be credited by the Trustee at 100% of the principal  amount thereof against
such  principal  payment,  provided  further  that in the case of a credit  with
respect  to  any  Authority   Bonds,  the  principal  amount  thereof  shall  be
established by an officers'  certificate  (as defined in the Amended  Indenture)
concurred in by the Authority  Bond Trustee,  included with the  above-mentioned
notice to the Trustee.  The principal amount of Bonds to be paid on the due date
of such  principal  payment  will be reduced by the amount of any such credit or
credits in respect of Bonds previously redeemed or delivered as provided above.

                                      -18-

<PAGE>

     Upon  cancellation  in full or in part of any of the  Authority  Bonds  (or
provision for payment thereof having been made in accordance with the provisions
of the  Authority  Bond  Indenture)  and  payment of all fees and charges of the
trustee thereunder,  such trustee shall deliver to the Trustee, for cancellation
a corresponding amount of Bonds remaining in its possession.

     Such  redemption in every case shall be effected  upon notice  delivered by
the Company at least 60 days prior to the date of redemption,  to the registered
owner of the Bonds at its  address  as the same  shall  appear  on the  transfer
register of the Company, all subject to the conditions of, and as more fully set
forth in, the Amended Indenture and Supplemental Indenture.

     In case an event of  default,  as defined in the Amended  Indenture,  shall
occur,  the  principal of all the bonds at any such time  outstanding  under the
Amended  Indenture  may be  declared  or may  become due and  payable,  upon the
conditions  and in the  manner  and  with the  effect  provided  in the  Amended
Indenture.  The Amended Indenture  provides that such declaration may in certain
events be waived by the holders of a majority in  principal  amount of the bonds
outstanding.

     This Bond shall not be  assignable or  transferable  except as permitted or
required  by  Section  12.13  of the  Authority  Bond  Indenture.  This  Bond is
exchangeable  by the registered  owner hereof,  in person or by duly  authorized
attorney,  on the books of the Company to be kept for that purpose at the office
of  the  Company  in the  City  of  St.  Louis,  Missouri,  upon  surrender  and
cancellation  of  this  Bond  and on  presentation  of a duly  executed  written
instrument of transfer, and thereupon a new Bond or Bonds of the same series, of
the same  aggregate  principal  amount and in authorized  denominations  will be
issued to the transferee or transferees in exchange herefor,  without payment of
any charge  other  than  stamp  taxes and other  governmental  charges  incident
thereto; and this Bond with or without others of like series, may in like manner
be  exchanged  for one or more new Bonds of the same series of other  authorized
denominations  but of the same aggregate  principal  amount;  all subject to the
terms and conditions set forth in the Amended Indenture.

     As provided in Section 7.04 of the Authority Bond Indenture, from and after
the Release Date (as defined in the Authority Bond  Indenture),  the obligations
of the Company  with  respect to this Bond shall be deemed to be  satisfied  and
discharged,  this  Bond  shall  cease to  secure  in any  manner  the  Company's
obligations  under the  Agreement  with respect to the payment of any  Authority
Bonds outstanding  under the Authority Bond Indenture,  and, pursuant to Section
7.04 of the Authority Bond Indenture, the Authority Bond Trustee shall forthwith
deliver this Bond to the Company for cancellation.

     No  recourse  shall be had for the  payment  of the  principal  of,  or the
interest  on,  this  Bond,  or for any  claim  based  hereon  or on the  Amended
Indenture or any indenture  supplemental thereto,  against any incorporator,  or
against any stockholder,  director or officer,  past,  present or future, of the
Company,  or of any  predecessor or successor  corporation,  either  directly or
through the Company or any such  predecessor or successor  corporation,  whether
for  amounts  unpaid on stock  subscriptions  or by virtue of any  constitution,
statute or rule of law, or by the  enforcement  of any  assessment or penalty or
otherwise, all such liability, whether at common law, in equity,

                                      -19-

<PAGE>

by any  constitution,  statute or  otherwise,  of  incorporators,  stockholders,
directors or officers  being released by every owner hereof by the acceptance of
this  Bond and as part of the  consideration  for the  issue  hereof,  and being
likewise released by the terms of the Amended Indenture.


                      [END OF FORM OF REVERSE OF NEW BOND]


                                   ARTICLE II

                             ISSUE OF THE NEW BONDS

     Section  2.1.  The  principal   amount  of  the  New  Bonds  which  may  be
authenticated  and  delivered  hereunder  is limited  to an amount  equal to the
principal  amount of Fifty  Million  Dollars  ($50,000,000)  consisting of Bonds
maturing on September 1, 2033.

     Section  2.2.  The New Bonds in the  aggregate  principal  amount set forth
above, may forthwith be executed by the Company and delivered to the Trustee and
shall be authenticated by the Trustee and delivered  (either before or after the
filing or recording hereof) to or upon the order of the Company, upon compliance
by the Company with the  applicable  provisions of Article III and Article XVIII
of the Original Indenture.

     Section 2.3. As provided in Section 7.04 of the Authority  Bond  Indenture,
from and after the Release Date (as defined in the  Authority  Bond  Indenture),
the  obligations of the Company with respect to the New Bonds shall be deemed to
be satisfied and  discharged,  the New Bonds shall cease to secure in any manner
the Company's obligations under the Agreement with respect to the payment of any
Authority Bonds outstanding under the Authority Bond Indenture, and, pursuant to
Section 7.04 of the Authority Bond  Indenture,  the Authority Bond Trustee shall
forthwith deliver the New Bonds to the Company for cancellation.


                                   ARTICLE III

                           REDEMPTION OF THE NEW BONDS

     Section 3.1. The New Bonds are,  subject to the  provisions of the Original
Indenture, subject to redemption in the amounts, at the times, at the prices and
under  the  circumstances  under  which  the  Authority  Bonds  are  subject  to
redemption,  under the same terms and conditions set forth in the Authority Bond
Indenture for the redemption of the Authority Bonds. In the event that less than
all the New Bonds are to be  redeemed,  the New  Bonds to be  redeemed  shall be
determined  by lot in such  manner as the Trustee in its  discretion  shall deem
proper, as in the Original Indenture provided.

     The New Bonds are also subject to mandatory  redemption as set forth in the
form of New Bonds in Section 1.3 of Article I of this Supplemental Indenture.

                                      -20-

<PAGE>

     Section  3.2.  Subject  to the  provisions  of  Article  V of the  Original
Indenture,  notice of  redemption  shall be delivered by the Company at least 60
days prior to the date of redemption,  to the registered  owner of such Bonds at
its address as the same shall appear on the transfer register of the Company.

     Section 3.3. As provided in the Authority  Bond  Indenture,  any amounts of
money held in the Bond Fund  provided in said  Indenture  and available for such
purpose,  which are at the request of the Company applied to the payments of the
principal  of,  premium,  if any,  and  interest on the  Authority  Bonds on any
payment or redemption  date,  shall be applied as a credit on amounts  otherwise
due under the New  Bonds;  provided  that the  amount  of such  credit  shall be
established by an officers'  certificate (as defined in the Amended  Indenture),
concurred in by the Authority Bond Trustee which shall be filed with the Trustee
prior to the application of any such credit.

     Upon  cancellation  in full or in part of any of the  Authority  Bonds  (or
provision for payment thereof having been made in accordance with the provisions
of the  Authority  Bond  Indenture)  and  payment of all fees and charges of the
trustee thereunder,  such trustee shall deliver to the Trustee, for cancellation
a corresponding amount of New Bonds remaining in its possession or shall request
such Trustee to issue a New Bond reflecting any such cancellation


                                   ARTICLE IV

                                    COVENANTS

     The Company hereby covenants, warrants and agrees;

     Section 4.1.  That the Company is lawfully  seized and  possessed of all of
the mortgaged  property  described in the granting clauses of this  Supplemental
Indenture;  that it has good right and lawful  authority to mortgage the same as
provided in this Supplemental Indenture; and that such mortgaged property is, at
the  actual  date of the issue of the New  Bonds,  free and clear of any deed of
trust,  mortgage,  lien,  charge or  encumbrance  thereon or affecting the title
thereto  prior to the  Original  Indenture,  except as set forth in the granting
clauses of the Original Indenture or this Supplemental Indenture.

     Section  4.2.  That,  so  long  as any of the New  Bonds  are  outstanding,
whenever any officers' certificate is required to be filed or deposited with the
Trustee  pursuant to Section 3(b) of Article III of the Original  Indenture upon
an application for the  authentication  of additional  Bonds pursuant to Article
III of the Original  Indenture,  such officers'  certificate  shall include,  in
addition to the matters  required to be stated therein by said Section 3(b), the
statement with respect to the net earnings of the Company available for interest
after property retirement  appropriations  required by Section 2 of Article V of
the Supplemental Indenture of July 1, 1956.

     Section 4.3.  That,  so long as any of the New Bonds are  outstanding,  the
Company will not apply for the  authentication  and delivery of additional Bonds
pursuant to Section 4 of Article III of the Original Indenture or the withdrawal
of cash from the trust estate or the reduction of the amount of cash required to
be paid into the trust  estate or to satisfy  the

                                      -21-

<PAGE>

maintenance and improvement funds under any provision of the Original  Indenture
or the Supplemental  Indentures  creating prior series of Bonds, on the basis of
the amount of $15,000,000 excluded from net bondable value of property additions
not subject to an unfunded  prior lien pursuant to Section 3 of Article V of the
Supplemental  Indenture  of October  1,  1945,  or on the basis of the amount of
$7,500,000 excluded from net bondable value of property additions not subject to
an unfunded  prior lien  pursuant to Section 3 of Article V of the  Supplemental
Indenture of July 1, 1956.

     Section 4.4.  That,  so long as any of the New Bonds are  outstanding,  the
Company will not issue or permit to be issued any prior lien bonds secured by an
unfunded prior lien in addition to the prior lien bonds secured by such unfunded
prior lien at the time of first  acquisition by the Company of property  subject
thereto  (other  than in lieu of  lost,  stolen  or  mutilated  bonds  or on the
exchange for bonds already  outstanding  of an equal  principal  amount of other
bonds of the same issue and the same series,  if any, and of the same maturity),
except upon  compliance  with the  provisions of Section 16 of Article IV of the
Original  Indenture,  nor unless the net earnings of the Company  available  for
interest after  property  retirement  appropriations  (determined as provided in
Section 2 of Article V of the  Supplemental  Indenture of July 1, 1956), for any
12  consecutive  calendar  months  during  the  period  of  15  calendar  months
immediately  preceding the first day of the month in which the additional  prior
lien bonds are to be issued, have been, in the aggregate, equal to not less than
twice the annual interest charges on the indebtedness specified in subparagraphs
(i) and (ii) of paragraph (1) of Section 2(a) of said Article V; provided  that,
if the application for the issue of such additional prior lien bonds is upon the
basis of payment at maturity of prior lien bonds  theretofore  sold or otherwise
disposed of or the  redemption or purchase  thereof after a date two years prior
to the date of maturity,  the additional  requirement  imposed by this Section 4
with  respect to net  earnings  of the  Company  available  for  interest  after
property retirement  appropriations  shall not apply. Any officers'  certificate
with  respect to net  earnings  of the  Company,  required  to be filed with the
Trustee as a  condition  precedent  to the issue of such  additional  prior lien
bonds, shall include, in addition to the matters otherwise required to be stated
therein, the matters required to be stated in an officers'  certificate pursuant
to paragraphs (1) and (2) of Section 2(a) of said Article V.

     Section 4.5.  That,  so long as any of the New Bonds are  outstanding,  the
Company will not acquire, by purchase, merger or otherwise, any property subject
to a lien or liens which will on  acquisition be an unfunded prior lien or prior
liens, except upon compliance with the provisions of Section 14 of Article IV of
the Original  Indenture,  nor unless the net earnings of such property available
for interest after property retirement appropriations  (determined in the manner
provided  in Section 2 of  Article V of the  Supplemental  Indenture  of July 1,
1956),  for any 12 consecutive  calendar months during the period of 15 calendar
months  immediately  preceding  the  first  day of the  month in which the first
acquisition of property subject to such lien or liens occurs,  have been, in the
aggregate,  equal to not less than twice the amount of annual interest  charges,
on all  outstanding  indebtedness  secured by such lien or liens.  Any officers'
certificate with respect to net earnings of such property,  required to be filed
with the Trustee as a condition  precedent to the  acquisition of such property,
shall  include,  in  addition  to the  matters  otherwise  required to be stated
therein, the matters required to be stated in an officers'  certificate pursuant
to Section 2 of said Article V applicable,  however, only to the net earnings of
such  property  and to the  indebtedness  secured  by such  liens to which  such
property is subject.

                                      -22-

<PAGE>


                                    ARTICLE V

                                   THE TRUSTEE

     The Trustee  hereby  accepts the trusts hereby  declared and provided,  and
agrees  to  perform  the same  upon the terms  and  conditions  in the  Original
Indenture and in this  Supplemental  Indenture set forth, and upon the following
terms and conditions:

     The Trustee shall not be  responsible  in any manner  whatsoever  for or in
respect of the validity or sufficiency of this Supplemental Indenture or the due
execution  hereof by the Company or for or in respect of the recitals  contained
herein, all of which recitals are made by the Company solely.


                                   ARTICLE VI

                            MISCELLANEOUS PROVISIONS

     Section 6.1.  Except as otherwise  defined  herein,  all terms contained in
this Supplemental  Indenture shall, for all purposes thereof,  have the meanings
given to such terms in Article I of the Original Indenture.

     Section 6.2. This Supplemental Indenture may be simultaneously  executed in
any number of counterparts, each of which when so executed shall be deemed to be
an original;  but such  counterparts  shall together  constitute but one and the
same instrument.

                                      -23-

<PAGE>




     IN  WITNESS   WHEREOF,   said  Union  Electric   Company  has  caused  this
Supplemental Indenture to be executed on its behalf by its Chairman of the Board
or President or one of its Vice  Presidents  and its corporate seal to be hereto
affixed  and said seal and this  Supplemental  Indenture  to be  attested by its
Secretary or one of its Assistant Secretaries; and said The Bank of New York, in
evidence  of its  acceptance  of the  trust  hereby  created,  has  caused  this
Supplemental  Indenture to be executed on its behalf by its  President or one of
its Vice  Presidents,  and its corporate seal to be hereto affixed and said seal
and this Supplemental  Indenture to be attested by its Secretary,  or one of its
Assistant Secretaries; all as of the 1st day of February, Two thousand and four.

Attested:                                UNION ELECTRIC COMPANY,
                                           1901 Chouteau Avenue
                                           St. Louis, Missouri  63103


/s/ G. L. Waters                         By: /s/ Jerre E. Birdsong
------------------------------------        ------------------------------------
              G. L. Waters               Name:   Jerre E. Birdsong
          Assistant Secretary            Title: Vice President and Treasurer


Signed, sealed and delivered by
       UNION ELECTRIC COMPANY
       in the presence of:


/s/ Daphyne Bradley
------------------------------------
                Daphyne Bradley


/s/ Wayne K. Forbes
------------------------------------
                Wayne K. Forbes

                As Witnesses


                                      -24-

<PAGE>



Attested:                                THE BANK OF NEW YORK,
                                           911 Washington Avenue
                                           St. Louis, Missouri  63101


/s/ Thomas Maple                         By: /s/ Robert J. Dunn
------------------------------------        ------------------------------------
                                         Name:   Robert J. Dunn
                                         Title:  As Agent


Signed, sealed and delivered by
       THE BANK OF NEW YORK
       in the presence of:


/s/ Daniel G. Dwyer
------------------------------------


/s/ Richard F. Novosak
------------------------------------

                  As Witnesses


                                      -25-

<PAGE>



STATE OF MISSOURI          )
                           )  SS:
CITY OF ST. LOUIS          )

     On this 17th day of February,  2004,  before me appeared JERRE E. BIRDSONG,
to me personally  known,  who,  being by me duly sworn,  did say that he is Vice
President and Treasurer of UNION ELECTRIC COMPANY,  a corporation,  and that the
seal  affixed  to  the  foregoing  instrument  is the  corporate  seal  of  said
corporation,  and that said  instrument  was signed and sealed in behalf of said
corporation  by authority of its Board of Directors,  and said JERRE E. BIRDSONG
acknowledged said instrument to be the free act and deed of said corporation.

     IN  TESTIMONY  WHEREOF,  I have  hereto set my hand and affixed my official
seal at my office, in the City and State aforesaid,  the day and year last above
written.


                                         /s/ S. A. Kitchens
                                         ---------------------------------------



<PAGE>







STATE OF MISSOURI          )
                           )  SS:
CITY OF ST. LOUIS          )

     On this 17th day of February, 2004, before me appeared Rober J. Dunn, to me
personally  known,  who, being by me duly sworn,  did say that he is an Agent of
THE BANK OF NEW YORK, a corporation,  and that the seal affixed to the foregoing
instrument is the corporate seal of said  corporation,  and that said instrument
was signed and sealed in behalf of said corporation,  as the trustee  thereunder
by authority of its Board of Directors,  and said Vice  President,  acknowledged
said  instrument to be the free act and deed of said  corporation as the trustee
under said instrument.

     IN  TESTIMONY  WHEREOF,  I have  hereto set my hand and affixed my official
seal at my office, in the City and State aforesaid,  the day and year last above
written.


                                         /s/ Sally Lardge
                                         ---------------------------------------