<PAGE>
                                                                   EXHIBIT 4-4-1


================================================================================


                             SUPPLEMENTAL INDENTURE

                                   ----------

                            Dated as of March 1, 2002

                                   ----------

                           COMMONWEALTH EDISON COMPANY

                                       to

                            BNY MIDWEST TRUST COMPANY

                                       and

                                  D. G. DONOVAN

             Trustees under Mortgage Dated July 1, 1923, and Certain
                         Indentures Supplemental Thereto

                                   ----------

                            Providing for Issuance of

                      FIRST MORTGAGE 6.15% BONDS, SERIES 98
                               DUE MARCH 15, 2012


================================================================================


<PAGE>




         THIS SUPPLEMENTAL INDENTURE, dated as of March 1, 2002, between
COMMONWEALTH EDISON COMPANY, a corporation organized and existing under the laws
of the State of Illinois (hereinafter called the "Company") having an address at
10 South Dearborn Street, 37th floor, Chicago, Illinois 60603, party of the
first part, and BNY MIDWEST TRUST COMPANY, a trust company organized and
existing under the laws of the State of Illinois having an address at 2 North
LaSalle Street, Suite 1020, Chicago, Illinois 60602, and D.G. DONOVAN, an
individual having an address at 2 North LaSalle Street, Suite 1020, Chicago,
Illinois 60602, as Trustee and Co-Trustee, respectively, under the Mortgage of
the Company dated July 1, 1923, as amended and supplemented by Supplemental
Indenture dated August 1, 1944 and the subsequent supplemental indentures
hereinafter mentioned, parties of the second part (said Trustee being
hereinafter called the "Trustee", the Trustee and said Co-Trustee being
hereinafter together called the "Trustees", and said Mortgage dated July 1,
1923, as amended and supplemented by said Supplemental Indenture dated August 1,
1944 and subsequent supplemental indentures, being hereinafter called the
"Mortgage"),

                              W I T N E S S E T H:

         WHEREAS, the Company duly executed and delivered the Mortgage to
provide for the issue of, and to secure, its bonds, issuable in series and
without limit as to principal amount except as provided in the Mortgage; and

         WHEREAS, the Company from time to time has executed and delivered
supplemental indentures to the Mortgage to provide for (i) the creation of
additional series of bonds secured by the Mortgage, (ii) the amendment of
certain of the terms and provisions of the Mortgage and (iii) the confirmation
of the lien of the Mortgage upon property of the Company, such supplemental
indentures that are currently effective and the respective dates, parties
thereto and purposes thereof, being as follows:

<TABLE>
<CAPTION>
    SUPPLEMENTAL
    INDENTURE DATE             PARTIES                                                  PROVIDING FOR
<S>                            <C>                                                      <C>
    August 1, 1944             Company to Continental Illinois National Bank            Amendment and restatement of
                               and Trust Company of Chicago and Edmond B.               Mortgage dated July 1, 1923
                               Stofft, as Trustee and Co-Trustee

    August 1, 1946             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Edmond B.
                               Stofft, as Trustee and Co-Trustee

    April 1, 1953              Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Edmond B.
                               Stofft, as Trustee and Co-Trustee

    March 31, 1967             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Edward J.
                               Friedrich, as Trustee and Co-Trustee

    April 1, 1967              Company to Continental Illinois National Bank            Amendment of Sections 3.01, 3.02,
                               and Trust Company of Chicago and                         3.05 and 3.14 of the
</TABLE>


                                      -1-

<PAGE>

<TABLE>
<CAPTION>
    SUPPLEMENTAL
    INDENTURE DATE             PARTIES                                                  PROVIDING FOR
<S>                            <C>                                                      <C>
                               Edward J. Friedrich, as Trustee and Co-Trustee           Mortgage and issuance of First Mortgage
                                                                                        5-3/8% Bonds, Series Y

    February 28, 1969          Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    May 29, 1970               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    June 1, 1971               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 1, 1972              Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    May 31, 1972               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    June 15, 1973              Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    May 31, 1974               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    June 13, 1975              Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    May 28, 1976               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    June 3, 1977               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    May 17, 1978               Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    August 31, 1978            Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    June 18, 1979              Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee
</TABLE>


                                      -2-

<PAGE>

<TABLE>
<CAPTION>
    SUPPLEMENTAL
    INDENTURE DATE             PARTIES                                                  PROVIDING FOR
<S>                            <C>                                                      <C>
    June 20, 1980              Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 16, 1981             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 30, 1982             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 15, 1983             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 13, 1984             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 15, 1985             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and Donald W.
                               Alfvin, as Trustee and Co-Trustee

    April 15, 1986             Company to Continental Illinois National Bank            Confirmation of mortgage lien
                               and Trust Company of Chicago and M.J. Kruger,
                               as Trustee and Co-Trustee

    June 15, 1990              Company to Continental Bank, National                    Issuance of First Mortgage 9-7/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 75
                               Co-Trustee

    June 1, 1991               Company to Continental Bank, National                    Issuance of First Mortgage Bonds,
                               Association and M.J. Kruger, as Trustee and              Pollution Control Series 1991
                               Co-Trustee

    October 1, 1991            Company to Continental Bank, National                    Issuance of First Mortgage 8-1/4%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 76 and First
                               Co-Trustee                                               Mortgage 8-7/8% Bonds, Series 77

    October 15, 1991           Company to Continental Bank, National                    Issuance of First Mortgage 8-3/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 78 and First
                               Co-Trustee                                               Mortgage 9-1/8% Bonds, Series 79

    February 1, 1992           Company to Continental Bank, National                    Issuance of First Mortgage 7%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 80 and First
                               Co-Trustee                                               Mortgage 8-5/8% Bonds, Series 81

    May 15, 1992               Company to Continental Bank, National                    Issuance of First Mortgage 6-1/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 82 and First
                               Co-Trustee                                               Mortgage 8% Bonds, Series 83
</TABLE>


                                      -3-

<PAGE>

<TABLE>
<CAPTION>
    SUPPLEMENTAL
    INDENTURE DATE             PARTIES                                                  PROVIDING FOR
<S>                            <C>                                                      <C>
    July 15, 1992              Company to Continental Bank, National                    Issuance of First Mortgage 8-1/2%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 84
                               Co-Trustee

    September 15, 1992         Company to Continental Bank, National                    Issuance of First Mortgage 7-3/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 85 and First
                               Co-Trustee                                               Mortgage 8-3/8% Bonds, Series 86

    February 1, 1993           Company to Continental Bank, National                    Issuance of First Mortgage 8-3/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 88
                               Co-Trustee

    April 1, 1993              Company to Continental Bank, National                    Issuance of First Mortgage 6-1/2%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 90 and First
                               Co-Trustee                                               Mortgage 8% Bonds, Series 91

    April 15, 1993             Company to Continental Bank, National                    Issuance of First Mortgage 7-5/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 92
                               Co-Trustee

    June 15, 1993              Company to Continental Bank, National                    Issuance of First Mortgage 7%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 93 and First
                               Co-Trustee                                               Mortgage 7-1/2% Bonds, Series 94

    July 15, 1993              Company to Continental Bank, National                    Issuance of First Mortgage 6-5/8%
                               Association and M.J. Kruger, as Trustee and              Bonds, Series 96 and First
                               Co-Trustee                                               Mortgage 7-3/4% Bonds, Series 97

    January 15, 1994           Company to Continental Bank, National                    Issuance of First Mortgage Bonds,
                               Association and M.J. Kruger, as Trustee and              Pollution Control Series 1994A,
                               Co-Trustee                                               1994B and 1994C

    December 1, 1994           Company to Bank of America Illinois and                  Issuance of First Mortgage Bonds,
                               Robert J. Donahue, as Trustee and Co-Trustee             Pollution Control Series 1994D

    June 1, 1996               Company to Harris Trust and Savings Bank and             Issuance of First Mortgage Bonds,
                               D.G. Donovan, as Trustee and Co-Trustee                  Pollution Control Series 1996A and
                                                                                        1996B
</TABLE>

         WHEREAS, the respective designations, maturity dates and principal
amounts of the bonds of each series presently outstanding under, and secured by,
the Mortgage and the several supplemental indentures above referred to, are as
follows:
<TABLE>
<CAPTION>
            DESIGNATION                                   MATURITY DATE                       PRINCIPAL AMOUNT
<S>                                                    <C>                                    <C>
First Mortgage 9-7/8% Bonds, Series 75                 June 15, 2020                           $   54,171,000

First Mortgage 8-1/4% Bonds, Series 76                 October 1, 2006                            100,000,000
</TABLE>


                                      -4-


<PAGE>

<TABLE>
<CAPTION>
            DESIGNATION                                   MATURITY DATE                       PRINCIPAL AMOUNT
<S>                                                    <C>                           <C>
First Mortgage 8-3/8% Bonds, Series 78                 October 15, 2006                           125,000,000

First Mortgage 8-5/8% Bonds, Series 81                 February 1, 2022                           200,000,000

First Mortgage 8% Bonds, Series 83                     May 15, 2008                               140,000,000

First Mortgage 8-1/2% Bonds, Series 84                 July 15, 2022                              200,000,000

First Mortgage 7-3/8% Bonds, Series 85                 September 15, 2002                         200,000,000

First Mortgage 8-3/8% Bonds, Series 86                 September 15, 2022                         200,000,000

First Mortgage 8-3/8% Bonds, Series 88                 February 15, 2023                          235,950,000

First Mortgage 8% Bonds, Series 91                     April 15, 2023                             160,000,000

First Mortgage 7-5/8% Bonds, Series 92                 April 15, 2013                             220,000,000

First Mortgage 7% Bonds, Series 93                     July 1, 2005                               225,000,000

First Mortgage 7-1/2% Bonds, Series 94                 July 1, 2013                               150,000,000

First Mortgage 6-5/8% Bonds, Series 96                 July 15, 2003                              100,000,000

First Mortgage 7-3/4% Bonds, Series 97                 July 15, 2023                              150,000,000

First Mortgage 5.3% Bonds, Pollution                   June 1, 2011                               100,000,000
Control Series 1991

First Mortgage 5.3% Bonds, Pollution                   January 15, 2004                            26,000,000
Control Series 1994A

First Mortgage 5.7% Bonds, Pollution                   January 15, 2009                            20,000,000
Control Series 1994B

First Mortgage 5.85% Bonds, Pollution                  January 15, 2014                            20,000,000
Control Series 1994C

First Mortgage 5.3% Bonds, Pollution                   March 1, 2015                               91,000,000
Control Series 1994D

First Mortgage 4.4% Bonds, Pollution                   December 1, 2006                           110,000,000
Control Series 1996A

First Mortgage 4.4% Bonds, Pollution Control Series    December 1, 2006                            89,400,000
Control Series 1996B
                                                                                     -------------------------
                                                       Total                                   $2,916,521,000
                                                                                     =========================
</TABLE>

         WHEREAS, the Mortgage provides for the issuance from time to time
thereunder, in series, of bonds of the Company for the purposes and subject to
the limitations therein specified; and

         WHEREAS, the Company desires, by this Supplemental Indenture, to create
an additional series of bonds to be issuable under the Mortgage, such bonds to
be designated "First Mortgage


                                      -5-

<PAGE>

6.15% Bonds, Series 98" (hereinafter called the "bonds of Series 98") and the
terms and provisions to be contained in the bonds of Series 98 or to be
otherwise applicable thereto to be as set forth in this Supplemental Indenture;
and

         WHEREAS, the bonds of Series 98 and the Trustee's certificate to be
endorsed thereon shall be substantially in the form of the General Form of
Registered Bond Without Coupons and the form of the General Form of Trustee's
Certificate set forth in Section 3.05 of the Supplemental Indenture dated August
1, 1944 to the Mortgage with such appropriate insertions, omissions and
variations in order to express the designation, date, maturity date, annual
interest rate, record dates for, and dates of, payment of interest,
denominations, terms of redemption and redemption prices, and other terms and
characteristics authorized or permitted by the Mortgage or not inconsistent
therewith; and

         WHEREAS, the Company is legally empowered and has been duly authorized
by the necessary corporate action and by order of the Illinois Commerce
Commission to make, execute and deliver this Supplemental Indenture, and to
create, as an additional series of bonds of the Company, the bonds of Series 98,
and all acts and things whatsoever necessary to make this Supplemental
Indenture, when executed and delivered by the Company and the Trustees, a valid,
binding and legal instrument, and to make the bonds of Series 98, when
authenticated by the Trustee and issued as in the Mortgage and in this
Supplemental Indenture provided, the valid, binding and legal obligations of the
Company, entitled in all respects to the security of the Mortgage, as amended
and supplemented, have been done and performed;

         NOW, THEREFORE, in consideration of the premises and of the sum of one
dollar duly paid by the Trustees to the Company, and for other good and valuable
consideration, the receipt of which is hereby acknowledged, the parties hereto
do hereby agree as follows:

         SECTION 1. DESIGNATION AND ISSUANCE OF BONDS OF SERIES 98. The bonds of
Series 98 shall, as hereinbefore recited, be designated as the Company's "First
Mortgage 6.15% Bonds, Series 98." Subject to the provisions of the Mortgage, the
bonds of Series 98 shall be issuable without limitation as to the aggregate
principal amount thereof.

         SECTION 2. FORM, DATE, MATURITY DATE, INTEREST RATE AND INTEREST
PAYMENT DATES OF BONDS OF SERIES 98. (a) The definitive bonds of Series 98 shall
be in engraved, lithographed, printed or typewritten form and shall be
registered bonds without coupons; and such bonds and the Trustee's certificate
to be endorsed thereon shall be substantially in the forms hereinbefore recited,
respectively. The bonds of Series 98 shall be dated as provided in Section 3.01
of the Mortgage, as amended by Supplemental Indenture dated April 1, 1967.

         (b) The bonds of Series 98 shall mature on March 15, 2012.

         (c) The bonds of Series 98 shall bear interest at the rate of 6.15% per
annum until the principal thereof shall be paid; provided, however, that if



                                      -6-

<PAGE>

                  (i) on or prior to the 270th day following the original issue
         date of the bonds of Series 98, neither (x) an exchange offer (the
         "Exchange Offer") registered pursuant to the Company's registration
         statement (the "Exchange Registration Statement") under the Securities
         Act of 1933, as amended (the "Securities Act"), registering a security
         substantially identical to the bonds of Series 98 (except that such
         security will not contain terms with respect to the Special Interest
         payments described below or the transfer restrictions described in
         Section 9(b) below) has been consummated nor (y) if applicable, in lieu
         thereof, a registration statement registering the bonds of Series 98
         for resale (a "Resale Registration Statement") has become or been
         declared effective; or

                  (ii) either the Exchange Registration Statement or, if
         applicable, the Resale Registration Statement is filed and declared
         effective, but shall thereafter cease to be effective or usable in
         accordance with and during the periods specified in the Registration
         Rights Agreement without being succeeded promptly by an additional
         registration statement filed and declared effective (subject to
         particular exceptions set forth in the Registration Rights Agreement),

in each case (i) and (ii) upon the terms and conditions set forth in the
Registration Rights Agreement (each such event referred to in clauses (i) and
(ii), a "Special Interest Payment Event"), then additional interest will accrue
(in addition to the interest stated above) (the "Step-Up") from the date of such
Special Interest Payment Event at a rate of 0.50% per annum, determined daily,
on the outstanding principal amount of the bonds of Series 98, and such
additional interest shall be payable until such time (the "Step Down Date") as
no Special Interest Payment Event is in effect or the first date the bonds of
Series 98 become freely tradable under Rule 144(k) of the Securities Act.
Interest accruing as a result of the Step-Up (which shall be computed on the
basis of a 365-day year and the actual number of days elapsed) is referred to
herein as "Special Interest." Any accrued and unpaid interest (including Special
Interest) on the bonds of Series 98 upon the issuance of New Securities (as
defined in the Registration Rights Agreement) in exchange for the bonds of
Series 98 subject to the provisions of this Section 2(c) shall cease to be
payable to the holders thereof but such accrued and unpaid interest (including
Special Interest) shall be payable on the next interest payment date for such
New Securities to the holders thereof on the related record date.

                  "Registration Rights Agreement" means the Registration Rights
         Agreement by and among the Company and the initial purchasers of the
         bonds of Series 98 regarding the Company's obligation to (1) complete
         the Exchange Offer and (2) register the resale of the bonds of Series
         98 with the United States Securities and Exchange Commission.

         (d) Interest on the bonds of Series 98 shall be payable semi-annually
on the fifteenth day of March and the fifteenth day of September in each year,
commencing September 15, 2002. March 1 and September 1 in each year are hereby
established as record dates for the payment of interest payable on the next
succeeding interest payment dates, respectively. The interest on each bond of
Series 98 so payable on any interest payment date shall, subject to the
exceptions provided in Section 3.01 of the Mortgage, as amended by said
Supplemental Indenture dated



                                      -7-

<PAGE>

April 1, 1967, be paid to the person in whose name such bond is registered at
the close of business on the March 1 or September 1, as the case may be, next
preceding such interest payment date.

         SECTION 3. EXECUTION OF BONDS OF SERIES 98. The bonds of Series 98
shall be executed on behalf of the Company by its President or one of its Vice
Presidents, manually or by facsimile signature, and shall have its corporate
seal affixed thereto or a facsimile of such seal imprinted thereon, attested by
its Secretary or one of its Assistant Secretaries, manually or by facsimile
signature, all as may be provided by resolution of the Board of Directors of the
Company. In case any officer or officers whose signature or signatures, manual
or facsimile, shall appear upon any bond of Series 98 shall cease to be such
officer or officers before such bond shall have been actually authenticated and
delivered, such bond nevertheless may be issued, authenticated and delivered
with the same force and effect as though the person or persons whose signature
or signatures, manual or facsimile, appear thereon had not ceased to be such
officer or officers of the Company.

         SECTION 4. MEDIUM AND PLACES OF PAYMENT OF PRINCIPAL OF AND INTEREST ON
BONDS OF SERIES 98; TRANSFERABILITY AND EXCHANGEABILITY. Both the principal of
and interest on the bonds of Series 98 shall be payable in any coin or currency
of the United States of America which at the time of payment is legal tender for
the payment of public and private debts, and both such principal and interest
shall be payable at the office or agency of the Company in the City of Chicago,
State of Illinois, or, at the option of the registered owner, at the office or
agency of the Company in the Borough of Manhattan, The City of New York, State
of New York, and such bonds shall be transferable and exchangeable, in the
manner provided in Sections 3.09 and 3.10 of the Mortgage, at said office or
agency. No charge shall be made by the Company to the registered owner of any
bond of Series 98 for the transfer of such bond or for the exchange thereof for
bonds of other authorized denominations, except, in the case of transfer, a
charge sufficient to reimburse the Company for any stamp or other tax or
governmental charge required to be paid by the Company or the Trustee.

         SECTION 5. DENOMINATIONS AND NUMBERING OF BONDS OF SERIES 98. The bonds
of Series 98 shall be issued in the denomination of $1,000 and in such multiples
of $1,000 as shall from time to time hereafter be determined and authorized by
the Board of Directors of the Company or by any officer or officers of the
Company authorized to make such determination, the authorization of the
denomination of any bond of Series 98 to be conclusively evidenced by the
execution thereof on behalf of the Company. Bonds of Series 98 shall be numbered
R-1 and consecutively upwards.

         SECTION 6. TEMPORARY BONDS OF SERIES 98. Until definitive bonds of
Series 98 are ready for delivery, there may be authenticated and issued in lieu
of any thereof and subject to all of the provisions, limitations and conditions
set forth in Section 3.11 of the Mortgage, temporary registered bonds without
coupons of Series 98.


                                      -8-

<PAGE>

         SECTION 7. REDEMPTION OF BONDS OF SERIES 98. (a) The bonds of Series 98
shall be redeemable, at the option of the Company, as a whole or in part, at any
time upon notice sent by the Company through the mail, postage prepaid, at least
thirty (30) days and not more than forty-five (45) days prior to the date fixed
for redemption, to the registered holder of each bond to be redeemed in whole or
in part, addressed to such holder at his address appearing upon the registration
books, at a redemption price equal to the greater of

                  (1) 100% of the principal amount of the bonds of Series 98 to
         be redeemed, plus accrued interest to the redemption date, or

                  (2) as determined by the Quotation Agent (as hereinafter
         defined), the sum of the present values of the remaining scheduled
         payments of principal and interest on the bonds of Series 98 to be
         redeemed (not including any portion of payments of interest accrued as
         of the redemption date) discounted to the redemption date on a
         semi-annual basis (assuming a 360-day year consisting of twelve 30-day
         months) at the Adjusted Treasury Rate (as hereinafter defined) plus
         twenty-five (25) basis points, plus accrued interest to the redemption
         date.

Unless the Company defaults in payment of the redemption price, on and after the
redemption date, interest will cease to accrue on the bonds of Series 98 or
portions of the bonds of Series 98 called for redemption.

         For purposes of the foregoing, the following terms shall have the
respective meanings set forth below:

                  "Adjusted Treasury Rate" means, with respect to any redemption
         date, the rate per year equal to the semi-annual equivalent yield to
         maturity of the Comparable Treasury Issue, assuming a price for the
         Comparable Treasury Issue (expressed as a percentage of its principal
         amount) equal to the Comparable Treasury Price for the redemption date.

                  "Business Day" means any day that is not a day on which
         banking institutions in New York City are authorized or required by law
         or regulation to close.

                  "Comparable Treasury Issue" means the United States Treasury
         security selected by the Quotation Agent as having a maturity
         comparable to the remaining term of the bonds of Series 98 that would
         be used, at the time of selection and in accordance with customary
         financial practice, in pricing new issues of corporate debt securities
         of comparable maturity to the remaining term of the bonds of Series 98.

                  "Comparable Treasury Price" means, with respect to any
         redemption date:

                           (i) the average of the Reference Treasury Dealer
                  Quotations for that redemption date, after excluding the
                  highest and lowest of the Reference Treasury Dealer
                  Quotations; or



                                      -9-
<PAGE>

                           (ii) if the Trustee obtains fewer than three
                  Reference Treasury Dealer Quotations, the average of all
                  Reference Treasury Dealer Quotations so received.

                  "Quotation Agent" means the Reference Treasury Dealer
         appointed by the Company.

                  "Reference Treasury Dealer" means (1) each of J.P. Morgan
         Securities Inc. and Salomon Smith Barney Inc. and their respective
         successors, unless any of them ceases to be a primary U.S. Government
         securities dealer in New York City (a "Primary Treasury Dealer"), in
         which case the Company shall substitute another Primary Treasury
         Dealer; and (2) any other Primary Treasury Dealer selected by the
         Company.

                  "Reference Treasury Dealer Quotations" means, with respect to
         each Reference Treasury Dealer and any redemption date, the average, as
         determined by the Trustee, of the bid and asked prices for the
         Comparable Treasury Issue (expressed in each case as a percentage of
         its principal amount) quoted in writing to the Trustee by that
         Reference Treasury Dealer at 5:00 p.m., New York City time, on the
         third Business Day preceding that redemption date.

         (b) In case the Company shall desire to exercise such right to redeem
and pay off all or any part of such bonds of Series 98 as hereinbefore provided,
it shall comply with all the terms and provisions of Article V of the Mortgage
applicable thereto, and such redemption shall be made under and subject to the
terms and provisions of Article V and in the manner and with the effect therein
provided, but at the time or times and upon mailing of notice, all as
hereinbefore set forth in this Section 7. No publication of notice of any
redemption of any bonds of Series 98 shall be required under Section 5.03(a) of
the Mortgage.

         SECTION 8. BOOK-ENTRY ONLY SYSTEM. It is intended that the bonds of
Series 98 be registered so as to participate in the securities depository system
(the "DTC System") with The Depository Trust Company ("DTC"), as set forth
herein. The bonds of Series 98 shall be initially issued in the form of a fully
registered bond or bonds in the name of Cede & Co., or any successor thereto, as
nominee for DTC. The Company and the Trustees are authorized to execute and
deliver such letters to or agreements with DTC as shall be necessary to
effectuate the DTC System, including the Letter of Representations from the
Company and the Trustees to DTC relating to the bonds of Series 98 (the
"Representation Letter"). In the event of any conflict between the terms of the
Representation Letter and the Mortgage, the terms of the Mortgage shall control.
DTC may exercise the rights of a bondholder only in accordance with the terms
hereof applicable to the exercise of such rights.

         With respect to bonds of Series 98 registered in the name of DTC or its
nominee, the Company and the Trustees shall have no responsibility or obligation
to any broker-dealer, bank or other financial institution for which DTC holds
such bonds from time to time as securities depository (each such broker-dealer,
bank or other financial institution being referred to herein as a "Depository
Participant") or to any person on behalf of whom such a Depository Participant



                                      -10-

<PAGE>

holds an interest in such bonds (each such person being herein referred to as an
"Indirect Participant"). Without limiting the immediately preceding sentence,
the Company and the Trustees shall have no responsibility or obligation with
respect to:

                  (i) the accuracy of the records of DTC, its nominee or any
         Depository Participant with respect to any ownership interest in the
         bonds of Series 98,

                  (ii) the delivery to any Depository Participant or any
         Indirect Participant or any other person, other than a registered owner
         of a bond of Series 98, of any notice with respect to the bonds of
         Series 98, including any notice of redemption,

                  (iii) the payment to any Depository Participant or Indirect
         Participant or any other person, other than a registered owner of a
         bond of Series 98, of any amount with respect to principal of,
         redemption premium, if any, on, or interest on, the bonds of Series 98,
         or

                  (iv) any consent given by DTC as registered owner.

So long as certificates for the bonds of Series 98 are not issued as hereinafter
provided, the Company and the Trustees may treat DTC or any successor securities
depository as, and deem DTC or any successor securities depository to be, the
absolute owner of such bonds for all purposes whatsoever, including, without
limitation, (1) the payment of principal and interest on such bonds, (2) giving
notice of matters (including redemption) with respect to such bonds and (3)
registering transfers with respect to such bonds. While a bond of Series 98 is
in the DTC System, no person other than DTC or its nominee shall receive a
certificate with respect to such bond.

         In the event that:

                  (a) DTC notifies the Company that it is unwilling or unable to
         continue as depositary or if DTC ceases to be a clearing agency
         registered under applicable law and a successor depositary is not
         appointed by the Company within 90 days,

                  (b) the Company determines that the beneficial owners of the
         bonds of Series 98 should be able to obtain certificated bonds and so
         notifies the Trustees in writing or

                  (c) there shall have occurred and be continuing a completed
         default or any event which after notice or lapse of time or both would
         be a completed default with respect to the bonds of Series 98,

the bonds of Series 98 shall no longer be restricted to being registered in the
name of DTC or its nominee. In the case of clause (a) of the preceding sentence,
the Company may determine that the bonds of Series 98 shall be registered in the
name of and deposited with a successor depository operating a securities
depository system, as may be acceptable to the Company and the Trustees, or such
depository's agent or designee, and if the Company does not appoint a



                                      -11-

<PAGE>

successor securities depository system within 90 days, then the bonds may be
registered in whatever name or names registered owners of bonds transferring or
exchanging such bonds shall designate, in accordance with the provisions hereof.

         Notwithstanding any other provision of the Mortgage to the contrary, so
long as any bond of Series 98 is registered in the name of DTC or its nominee,
all payments with respect to principal of and interest on such bond and all
notices with respect to such bond shall be made and given, respectively, in the
manner provided in the Representation Letter.

         SECTION 9. LEGENDS. (a) So long as the bonds of Series 98 are held by
the Depository Trust Company, such bonds of Series 98 shall bear the following
legend:

                  Unless this bond is presented by an authorized representative
         of the Depository Trust Company, a New York corporation ("DTC"), to the
         Company or its agent for registration of transfer, exchange or payment,
         and any bond issued is registered in the name of Cede & Co. or in such
         other name as is requested by an authorized representative of DTC (and
         any payment is made to Cede & Co. or to such other entity as is
         requested by an authorized representative of DTC), any transfer, pledge
         or other use hereof for value or otherwise by a person is wrongful
         inasmuch as the registered owner hereof, Cede & Co., has an interest
         herein.

         (b) The bonds of Series 98 are initially being issued without
registration under the Securities Act in reliance on Rule 144A under the
Securities Act. Accordingly, until such time as the bonds of Series 98 are
registered under the Securities Act, or are exchanged for securities
substantially identical to the bonds of Series 98 (except that such securities
will not contain terms with respect to the Special Interest payments described
in Section 2(c) above or the transfer restrictions described herein) that are so
registered, the bonds of Series 98 shall bear the following legend:

                  This bond (or its predecessor) was originally issued in a
         transaction exempt from registration under the United States Securities
         Act of 1933, as amended ("Securities Act"), and may not be offered,
         sold, pledged or otherwise transferred in the absence of such
         registration or an applicable exemption therefrom and in any event may
         be sold or otherwise transferred only in accordance with the Mortgage,
         copies of which are available for inspection at the office of the
         Mortgage Trustee in the City of Chicago, Illinois.

                  Each purchaser of this bond is hereby notified that the seller
         may be relying on the exemption from the provisions of section 5 of the
         Securities Act provided by Rule 144A thereunder. Each holder of this
         bond represents to Commonwealth Edison Company that (a) such holder
         will not sell, pledge or otherwise transfer this bond (without the
         consent of Commonwealth Edison Company) other than (1) to a qualified
         institutional buyer in a transaction complying with Rule 144A under the
         Securities Act, (2) in accordance with Rule 144 under the Securities
         Act, (3) outside the United States in a transaction meeting the
         requirements of Regulation S under the Securities Act, (4) pursuant to
         another




                                      -12-

<PAGE>

         available exemption from registration under the Securities Act,
         subject, in the case of clauses (2), (3) or (4), to the receipt by
         Commonwealth Edison Company of an opinion of counsel or such other
         evidence acceptable to Commonwealth Edison Company that such resale,
         pledge or transfer is exempt from the registration requirements of the
         Securities Act or (5) pursuant to an effective registration statement
         and that (b) the holder will, and each subsequent holder is required
         to, notify any purchaser of this bond of the resale restrictions
         referred to herein and deliver to the transferee (other than a
         qualified institutional buyer) prior to the sale a copy of the transfer
         restrictions applicable hereto (copies of which may be obtained from
         the Mortgage Trustee).

         SECTION 10. CONFIRMATION OF LIEN. The Company, for the equal and
proportionate benefit and security of the holders of all bonds at any time
issued under the Mortgage, hereby confirms the lien of the Mortgage upon, and
hereby grants, bargains, sells, transfers, assigns, pledges, mortgages, warrants
and conveys unto the Trustees, all property of the Company and all property
hereafter acquired by the Company, other than (in each case) property which, by
virtue of any of the provisions of the Mortgage, is excluded from such lien, and
hereby confirms the title of the Trustees (as set forth in the Mortgage) in and
to all such property. Without in any way limiting or restricting the generality
of the foregoing, there is specifically included within the confirmation of lien
and title hereinabove expressed the property of the Company legally described on
Exhibit A attached hereto and made a part hereof.

         SECTION 11. MISCELLANEOUS. The terms and conditions of this
Supplemental Indenture shall be deemed to be a part of the terms and conditions
of the Mortgage for any and all purposes. The Mortgage, as supplemented by said
indentures supplemental thereto dated subsequent to August 1, 1944 and referred
to in the recitals of this Supplemental Indenture, and as further supplemented
by this Supplemental Indenture, is in all respects hereby ratified and
confirmed.

         This Supplemental Indenture shall bind and, subject to the provisions
of Article XIV of the Mortgage, inure to the benefit of the respective
successors and assigns of the parties hereto.

         Although this Supplemental Indenture is dated as of March 1, 2002, it
shall be effective only from and after the actual time of its execution and
delivery by the Company and the Trustees on the date indicated by their
respective acknowledgments hereto annexed.

         This Supplemental Indenture may be simultaneously executed in any
number of counterparts, and all such counterparts executed and delivered, each
as an original, shall constitute but one and the same instrument.



                                      -13-

<PAGE>


                  IN WITNESS WHEREOF, Commonwealth Edison Company has caused
this Supplemental Indenture to be executed in its name by its Vice President and
Treasurer, and its seal to be hereunto affixed and attested by one of its
Assistant Secretaries, and BNY Midwest Trust Company, as Trustee under the
Mortgage, has caused this Supplemental Indenture to be executed in its name by
one of its Vice Presidents, and its seal to be hereunto affixed and attested by
one of its Assistant Secretaries, and D. G. Donovan, as Co-Trustee under the
Mortgage, has hereunto affixed his signature, all as of the day and year first
above written.


                                              COMMONWEALTH EDISON COMPANY


                                              By
                                                   J. Barry Mitchell
                                                   Vice President and Treasurer

(SEAL)

ATTEST:


         Scott N. Peters
         Assistant Secretary

                                              BNY MIDWEST TRUST COMPANY


                                              By
                                                   J. Bartolini
                                                   Vice President

(SEAL)

ATTEST:


         C. Potter
         Assistant Secretary


                                              D. G. DONOVAN




                                      -14-

<PAGE>







STATE OF ILLINOIS )
                           ) SS.
COUNTY OF COOK    )



         I, MARY L. KWILOS, a Notary Public in and for said County, in the State
aforesaid, DO HEREBY CERTIFY that J. BARRY MITCHELL, Vice President and
Treasurer of Commonwealth Edison Company, an Illinois corporation, one of the
parties described in and which executed the foregoing instrument, and SCOTT N.
PETERS, an Assistant Secretary of said corporation, who are both personally
known to me to be the same persons whose names are subscribed to the foregoing
instrument as such Vice President and Treasurer and Assistant Secretary,
respectively, and who are both personally known to me to be Vice President and
Treasurer and an Assistant Secretary, respectively, of said corporation,
appeared before me this day in person and severally acknowledged that they
signed, sealed, executed and delivered said instrument as their free and
voluntary act as such Vice President and Treasurer and Assistant Secretary,
respectively, of said corporation, and as the free and voluntary act of said
corporation, for the uses and purposes therein set forth.

         GIVEN under my hand and notarial seal this 6th day of March, A.D. 2002.






                                                         Mary L. Kwilos
                                                         Notary Public

(NOTARIAL SEAL)


My Commission expires October 26, 2005.





                                      -15-

<PAGE>





STATE OF ILLINOIS )
                            ) SS.
COUNTY OF COOK    )


         I, LINDA ELLEN GARCIA, a Notary Public in and for said County, in the
State aforesaid, DO HEREBY CERTIFY that J. BARTOLINI, a Vice President of BNY
Midwest Trust Company, an Illinois trust company, one of the parties described
in and which executed the foregoing instrument, and C. POTTER, an Assistant
Secretary of said trust company, who are both personally known to me to be the
same persons whose names are subscribed to the foregoing instrument as such Vice
President and Assistant Secretary, respectively, and who are both personally
known to me to be a Vice President and an Assistant Secretary, respectively, of
said trust company, appeared before me this day in person and severally
acknowledged that they signed, sealed, executed and delivered said instrument as
their free and voluntary act as such Vice President and Assistant Secretary,
respectively, of said trust company, and as the free and voluntary act of said
trust company, for the uses and purposes therein set forth.

         GIVEN under my hand and notarial seal this 6th day of March, A.D. 2002.





                                                         Linda Ellen Garcia
                                                         Notary Public

(NOTARIAL SEAL)


My Commission expires September 23, 2002.



                                      -16-

<PAGE>




STATE OF ILLINOIS )
                            ) SS.
COUNTY OF COOK    )




         I, LINDA ELLEN GARCIA, a Notary Public in and for said County, in the
State aforesaid, DO HEREBY CERTIFY that D. G. DONOVAN, one of the parties
described in and which executed the foregoing instrument, who is personally
known to me to be the same person whose name is subscribed to the foregoing
instrument, appeared before me this day in person and acknowledged that he
signed, executed and delivered said instrument as his free and voluntary act for
the uses and purposes therein set forth.

         GIVEN under my hand and notarial seal this 6th day of March, A.D. 2002.






                                                       Linda Ellen Garcia
                                                       Notary Public

(NOTARIAL SEAL)


My Commission expires September 23, 2002.




                                      -17-

<PAGE>


                                    EXHIBIT A

                               LEGAL DESCRIPTIONS


                                    [omitted]


                                      -18-