Document:

<Page>

                                                                 Exhibit 10.84.2
                                                                  EXECUTION COPY

                                  AMENDMENT TWO

            AMENDMENT TWO (this "AMENDMENT") dated as of May 30, 2001 by and
among EDISON MISSION ENERGY (the "BORROWER"), BANK OF AMERICA, N.A., as
Administrative Agent (in such capacity, the "ADMINISTRATIVE AGENT") and each
of certain commercial lending institutions party hereto (the "LENDERS").

            WHEREAS, the Borrower, the Administrative Agent and certain of
the Lenders entered into a Credit Agreement dated as of May 30, 2000 (as
amended by Amendment One dated as of August 17, 2000 among the Borrower, the
Administrative Agent and the Lenders party thereto, the "CREDIT AGREEMENT");

            WHEREAS, the Borrower has requested that the Lenders renew their
Commitments and extend the Commitment Termination Date to October 10, 2001.

            ACCORDINGLY, the parties hereto agree as follows:

            Section 1. DEFINITIONS. Except as otherwise defined in this
Amendment, terms defined in the Credit Agreement are used herein (and in the
introductions and recitals hereto) as defined therein.

            Section 2. AMENDMENT TO THE CREDIT AGREEMENT. Subject to the
satisfaction of the conditions precedent specified in Section 3 below, but
effective as of the Amendment Effective Date, the Credit Agreement shall be
amended as follows:

            (a) SECTION 1.1 of the Credit Agreement shall be amended by
deleting the definition of "CHANGE IN CONTROL" in its entirety.

            (b) SECTION 1.1 of the Credit Agreement shall be amended by
deleting CLAUSE (a) of the definition of "COMMITMENT TERMINATION DATE" in its
entirety and replacing it with the following:

                        "(a) October 10, 2001 or, if such date has been extended
            by any Lender pursuant to SECTION 2.6, then, with respect to the
            Commitment of such Lender, such date as determined pursuant to
            SECTION 2.6;".

            (c) SECTION 1.1 of the Credit Agreement shall be amended by adding
the following definitions in alphabetical order:

                        ""AMENDMENT EFFECTIVE DATE" shall have the meaning
            assigned to such term in Section 3 of Amendment Two to this
            Agreement.

                        "CAPITAL STOCK" means, with respect to any Person, any
            and all shares, interests, participations or other equivalents
            (however designated, whether voting or non-voting) of, or interests
            in (however designated), the equity of such

<Page>

                                       2

            Person, including, without limitation, all common stock and
            preferred stock and partnership and joint venture interests of
            such Person.

                        "CONSOLIDATED NET WORTH" means, at any date, the
            consolidated stockholders' equity of the Borrower and its
            Consolidated Subsidiaries determined as of such date without giving
            effect to any accumulated other comprehensive gain or loss after
            December 31, 1999 plus, to the extent not otherwise included
            therein, (a) the liquidation preference at such date of
            non-redeemable preferred stock of the Borrower and (b) Equity
            Preferred Securities.

                        "CONSOLIDATED OPERATING PROJECTS" means any electric
            generation facilities, oil and gas properties, trading activities,
            and operation and maintenance services in which the Borrower or its
            Subsidiaries have a direct or indirect ownership greater than 50%.

                        "CONSOLIDATED SUBSIDIARY" means, at any date with
            respect to any Person, any Subsidiary of such Person or other entity
            the accounts of which would be consolidated with those of such
            Person in its consolidated financial statements if such statements
            were prepared as of such date.

                        "DERIVATIVES OBLIGATIONS" of any Person means all
            obligations of such Person in respect of any rate swap transaction,
            basis swap, forward rate transaction, commodity swap, commodity
            option, equity or equity index swap, equity or equity index option,
            bond option, interest rate option, foreign exchange transaction, cap
            transaction, floor transaction, collar transaction, currency swap
            transaction, cross-currency rate swap transaction, currency option
            or any other similar transaction (including any option with respect
            to any of the foregoing transactions) or any combination of the
            foregoing transactions. For purposes of determining the Recourse
            Debt to Recourse Capital Ratio on any date, the Derivatives
            Obligations of the Borrower shall be determined on a "mark to
            market" basis on such date.

                        "DISTRIBUTIONS" means any interest or principal payments
            on loans, distributions, management fees and dividends to the
            Borrower or any of its Subsidiaries made by a Non-Consolidated
            Operating Project.

                        "EME REVOLVERS" means, collectively, the Credit
            Agreement, the March Credit Agreement and the October Credit
            Agreement.

                        "EQUITY PREFERRED SECURITIES" means securities issued by
            the Borrower (a) that are not subject to mandatory redemption or the
            underlying securities, if any, of which are not subject to mandatory
            redemption, (b) that are perpetual or mature no less than 30 years
            from the date of issuance, (c) the indebtedness issued in connection
            with which, including any guaranty, is subordinate in right of
            payment to the unsecured and unsubordinated indebtedness of the
            issuer of such indebtedness or guaranty, and (d) the terms of which
            permit

                                 AMENDMENT TWO
<Page>

                                       3

            the deferral of payment of interest or distributions thereon to the
            date occurring after the Commitment Termination Date.

                        "FUNDS FLOW FROM OPERATIONS" means, for any period,
            Distributions plus Operating Cash Flow plus interest income during
            such period less Operating Expenses during such period.

                        "INTEREST COVERAGE RATIO" means, for any period, the
            ratio of (a) Funds Flow from Operations during such period to (b)
            Interest Expense for such period.

                        "INTEREST EXPENSE" means the accrued interest expense of
            all the Borrower's senior recourse indebtedness, but shall exclude
            any intercompany obligation on which interest or the equivalent is
            received by the Borrower.

                        "MAJOR PROJECTS" means the First Hydro plant, the Loy
            Yang B plant, the Homer City Generating Station, the plants located
            in Illinois owned by Midwest Generation, LLC, the Kern River
            cogeneration facility, the Midway Sunset cogeneration facility, the
            Watson cogeneration facility and the Sycamore cogeneration facility.

                        "MARCH CREDIT AGREEMENT" means the $595,000,000 Credit
            Agreement dated as of March 18, 1999 among the Borrower, certain
            commercial lending institutions party thereto and Citicorp USA, Inc.
            as the administrative agent.

                        "MIDWEST" means Midwest Generation, LLC.

                        "NET CASH PROCEEDS" means (a) in connection with an
            asset disposition permitted under SECTION 7.2.7, the cash proceeds
            received from such asset disposition by the Borrower on an after-tax
            basis, net of attorney's fees, investment banking fees, accountants'
            fees, underwriting discounts and commissions and other customary
            fees and expenses actually incurred in connection therewith and (b)
            in connection with any issuance or sale of indebtedness or Capital
            Stock, the cash proceeds received from such issuance or incurrence
            on an after-tax basis, net of attorney's fees, investment banking
            fees, accountants' fees, underwriting discounts and commissions and
            other customary fees and expenses actually incurred in connection
            therewith.

                        "NON-CONSOLIDATED OPERATING PROJECTS" means any electric
            generation facilities, oil and gas properties, trading activities,
            and operation and maintenance services in which the Borrower or its
            Subsidiaries have a direct or indirect ownership equal to or less
            than 50%.

                        "OCTOBER CREDIT AGREEMENT" means the $425,000,000 Credit
            Agreement dated as of October 11, 1996 among the Borrower, certain
            commercial lending institutions party thereto and Bank of America,
            N.A. (formerly, Bank of America National Trust and Savings
            Association) as the administrative agent.

                                 AMENDMENT TWO
<Page>

                                       4

                        "OPERATING CASH FLOW" means, for any period, the excess
            of accrued Project Revenues during such period less accrued Project
            Operating Expenses less accrued Project Debt Service during such
            period from the Consolidated Operating Projects.

                        "OPERATING EXPENSES" means, for any period, all amounts
            accrued by the Borrower in the conduct of its business during such
            period, including utilities, general and administrative expenses,
            employee salaries, wages and other employment-related costs, fees
            for letters of credit, surety bonds and performance bonds. Operating
            Expenses do not include federal and state taxes, depreciation or
            amortization, and other non-cash charges.

                        "POWERTON/JOLIET GUARANTEES" means, collectively, (i)
            the Guaranty Agreement dated as of August 17, 2000 made by the
            Borrower in favor of Powerton Trust I that, among other things,
            guarantees the payment by Midwest of certain liabilities payable to
            Powerton Trust I, (ii) the Guaranty Agreement dated as of August 17,
            2000 made by the Borrower in favor of Powerton Trust II that, among
            other things, guarantees the payment by Midwest of certain
            liabilities payable to Powerton Trust II, (iii) the Guaranty
            Agreement dated as of August 17, 2000 made by the Borrower in favor
            of Joliet Trust I that, among other things, guarantees the payment
            by Midwest of certain liabilities payable to Joliet Trust I and (iv)
            the Guaranty Agreement dated as of August 17, 2000 made by the
            Borrower in favor of Joliet Trust II that, among other things,
            guarantees the payment by Midwest of certain liabilities payable to
            Joliet Trust II.

                        "POWERTON/JOLIET INTERCOMPANY NOTES" means the
            promissory notes of the Borrower dated as of August 24, 2000 having
            an aggregate principal amount equal to $1,367,000,000, evidencing in
            each case a loan from Midwest to the Borrower.

                        "PROJECT DEBT SERVICE" means, for any period, all
            accrued interest and principal payments during such period for the
            Consolidated Operating Projects. Any principal payments made due to
            refinancing shall be excluded.

                        "PROJECT OPERATING EXPENSES" means all accrued expenses
            by the Consolidated Operating Projects which are necessary for the
            continued operation and maintenance of the Consolidated Operating
            Projects which shall include operating lease payments and foreign
            taxes paid but exclude depreciation and amortization or any capital
            expenditure undertaken primarily to increase the efficiency of,
            expand or re-power the Consolidated Operating Projects or capital
            expenditures for environmental purposes which are not required by
            applicable law.

                        "PROJECT REVENUES" means, for any period, all accrued
            revenues by the Consolidated Operating Projects during such period,
            including revenues from the sale of energy and capacity, steam and
            fuel plus accruals for business interruption insurance and all
            interest and other income.

                                 AMENDMENT TWO
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                                       5

                        "RECOURSE DEBT" means, on any date, the sum (without
            duplication) of the following indebtedness of the Borrower: (a) all
            indebtedness for borrowed money other than Subordinated Debt; (b)
            all guarantees for (i) indebtedness of the Subsidiaries and (ii)
            rental expenses of the Subsidiaries; (c) all reimbursement
            obligations with respect to surety bonds, letters of credit (to the
            extent not collateralized with cash or Cash Equivalent Investments),
            bankers' acceptances and similar instruments (in each case, whether
            or not matured); (d) all obligations evidenced by notes, bonds,
            debentures or similar instruments, including obligations so
            evidenced incurred in connection with the acquisition of property,
            assets or businesses; and (e) Derivative Obligations. For purposes
            of the foregoing, (i) indebtedness of the Borrower shall exclude, to
            the extent included, (A) indebtedness of the Borrower evidenced by
            the Powerton/Joliet Intercompany Notes for so long as amounts
            payable thereunder are subject to setoff against amounts paid under
            the Powerton/Joliet Guarantees in accordance with the terms of the
            Powerton/Joliet Intercompany Notes; (B) indebtedness of the Borrower
            evidenced by the Synthetic Lease Intercompany Note for so long as
            amount payable thereunder are subject to setoff against payments
            under the Synthetic Lease Guarantee in accordance with the terms of
            the Synthetic Lease Intercompany Note; and (C) indebtedness of the
            Borrower under guarantees of rental expenses to the extent
            attributable to lease indebtedness provided by Subsidiaries under
            leasing transactions, including, without limitation, indebtedness of
            the Borrower under the Synthetic Lease Guarantee to the extent
            attributable to lease indebtedness provided by Subsidiaries as
            Synthetic Lease Tranche A Loans; and (ii) the amount of indebtedness
            of the Borrower under guarantees of rental expenses of the
            Subsidiaries on any date of determination shall be the termination
            value under the related lease on such date of determination
            (adjusted so as to give effect to adjustments contemplated by clause
            (i)(C) above, if applicable) plus reasonably anticipated indemnity
            or other similar payments as of such date of determination; provided
            that the amount of indebtedness of the Borrower under each
            Powerton/Joliet Guarantee on any date of determination shall be the
            Termination Value (or, if applicable, Special Termination Value) as
            defined in such Powerton/Joliet Guarantee on such date of
            determination plus reasonably anticipated indemnity or other similar
            payments as of such date of determination.

                        "RECOURSE DEBT TO RECOURSE CAPITAL RATIO" means, on any
            date, the ratio of: (a) Recourse Debt on such date to (b) the sum on
            such date of (i) Consolidated Net Worth on such date PLUS (ii)
            Recourse Debt.

                        "SYNTHETIC LEASE CREDIT AGREEMENT" means the Credit
            Agreement dated as of June 23, 2000 among EME/CDL Trust, Midwest
            Peaker Holdings, Inc., Citicorp Del-Lease, Inc. and Citicorp North
            America, Inc.

                        "SYNTHETIC LEASE GUARANTEE" means the Guaranty Agreement
            dated as of June 23, 2000 made by the Borrower in favor of the
            EME/CDL Trust.

                        "SYNTHETIC LEASE INTERCOMPANY NOTE" means the
            intercompany

                                 AMENDMENT TWO
<Page>

                                       6

            note of the Borrower dated as of July 10, 2000 having a principal
            amount of $300,000,000, evidencing a loan from Midwest to the
            Borrower.

                        "SYNTHETIC LEASE TRANCHE A LOANS" means the Tranche A
            Loans (as defined in the Synthetic Lease Credit Agreement).".

            (d) SECTION 2.2 of the Credit Agreement shall be amended by deleting
Section 2.2 in its entirety and replacing it with the following:

                        "REDUCTION OF THE TOTAL COMMITMENT AMOUNT. (a) The
            Borrower may, from time to time on any Business Day occurring after
            the Effective Date, voluntarily reduce the Total Commitment Amount
            without premium or penalty (subject, however, to SECTION 4.5);
            PROVIDED, HOWEVER, that all such reductions shall require at least
            one Business Days' prior notice to the Administrative Agent and be
            permanent, and any partial reduction of the Total Commitment Amount
            shall be in a minimum amount of $10,000,000 and in an integral
            multiple of $1,000,000 in excess thereof; and, PROVIDED, FURTHER,
            that the Total Commitment Amount may not be reduced to an amount
            less than the aggregate amount of outstanding Loans; and (b) as of
            August 15, 2001, in the event that the Total Commitment Amount is
            greater than $200,000,000, Commitments shall be reduced in an amount
            equal to the difference between the Total Commitment Amount and
            $200,000,000.".

            (e) SECTION 3.1.1 of the Credit Agreement shall be amended by
deleting Section 3.1.1(b) in its entirety and replacing it with the following:

                        "(b) the Borrower shall (i) immediately upon any
            acceleration of any Loans pursuant to SECTION 8.2 or SECTION 8.3,
            repay all Loans, unless, pursuant to SECTION 8.3, only a portion of
            all Loans is so accelerated; (ii) within three Business Days
            following the receipt of proceeds from (A) any sale or other
            disposition of assets not in the ordinary course of business, make a
            prepayment of the loans outstanding under the EME Revolvers, pro
            rata based on the total commitment amounts outstanding under each
            EME Revolver, in an aggregate amount in total equal to the lesser of
            (x) 50% of the related Net Cash Proceeds or (y) the aggregate
            principal amount of the loans under all of the EME Revolvers then
            outstanding (and the commitments under the EME Revolvers shall
            automatically be reduced, pro rata based on the total commitment
            amounts outstanding under the EME Revolvers, by an amount in total
            equal to 50% of the related Net Cash Proceeds) or (B) the sale or
            issuance of any Capital Stock or Indebtedness of the Borrower after
            the Amendment Effective Date, make a prepayment of the loans
            outstanding under the EME Revolvers, pro rata based on the total
            commitment amounts outstanding under each EME Revolver, in an
            aggregate amount in total equal to the lesser of (x) 100% of the
            related Net Cash Proceeds or (y) the aggregate principal amount of
            the loans under all of the EME Revolvers then outstanding (and the
            commitments under the EME Revolvers shall automatically be reduced,
            pro rata based on the total commitment amounts outstanding under
            each EME Revolver, by an aggregate amount in total equal to

                                 AMENDMENT TWO
<Page>

                                       7

            100% of the related Net Cash Proceeds); PROVIDED, HOWEVER, that the
            prepayment requirement under this SECTION 3.1.1(b)(ii) shall not be
            in effect if the Borrower has permanently reduced its outstanding
            commitments and loans under the EME Revolvers to an amount in the
            aggregate equal to or less than $850,000,000; and (iii) on August
            15, 2001 in the event the Loans outstanding exceed $200,000,000 as
            of such date, the Borrower shall prepay Loans in an amount equal to
            the difference between the Loans outstanding on such date and
            $200,000,000.".

            (f) SECTION 7.1.1 of the Credit Agreement shall be amended by
deleting Section 7.1.1(c) in its entirety and replacing it with the following:

                        "(c) concurrently with the delivery of financial
            statements referred to in SECTIONS 7.1.1.(a) AND 7.1.1(b), a
            certificate, executed by the controller, treasurer or chief
            financial officer of the Borrower, showing (in reasonable detail and
            with appropriate calculations and computations in all respects
            satisfactory to the Administrative Agent) compliance with the
            financial covenants set forth in SECTION 7.2.10 and SECTION
            7.2.11.".

            (g) SECTION 7.2.1 of the Credit Agreement shall be amended by
deleting Section 7.2.1(b) in its entirety and replacing it with the following:

                        "(b) (i) Capitalized Lease Liabilities, (ii) other
            secured Indebtedness of any kind whatsoever existing on the
            Amendment Effective Date and (iii) after the Amendment Effective
            Date, other secured Indebtedness, not to exceed $100,000,000 in the
            aggregate; PROVIDED that any secured Indebtedness exceeding such
            amount may be secured pursuant to SECTION 7.2.3(f); and".

            (h) SECTION 7.2.3 of the Credit Agreement shall be amended by
deleting Section 7.2.3(f) and replacing it with the following:

                        "(f) Liens upon any property (other than direct or
            indirect ownership interests of the Borrower in Major Projects,
            except for those Liens on such ownership interests existing on the
            Amendment Effective Date) at any time directly owned by the Borrower
            to secure any Indebtedness of the nature described in CLAUSE (b) of
            SECTION 7.2.1; and".

            (i) SECTION 7.2.4 of the Credit Agreement shall be amended by
deleting Section 7.2.4 in its entirety and replacing it with the following:

            "[INTENTIONALLY OMITTED]".

            (j) SECTION 7.2.6 of the Credit Agreement shall be amended by
deleting the parenthetical "(including, without limitation, a Change in
Control)" following the word "thereto" in the second line of Section 7.2.6(c) of
the Credit Agreement.

            (k) SECTION 7.2 of the Credit Agreement shall be amended by adding
the following sections:

                                 AMENDMENT TWO
<Page>

                                       8

                        "Section 7.2.10 INTEREST COVERAGE. The Borrower will at
            the end of each of its fiscal quarters maintain an Interest Coverage
            Ratio for the immediately preceding four consecutive fiscal quarters
            of the Borrower of not less than 1.50 to 1.00.

                        Section 7.2.11 RECOURSE DEBT TO RECOURSE CAPITAL RATIO.
            The Borrower will at the end of each of its fiscal quarters maintain
            a Recourse Debt to Recourse Capital Ratio of not more than 0.675 to
            1.00.".

            (l) SECTION 8.1.5 of the Credit Agreement shall be amended by
deleting Section 8.1.5 in its entirety and replacing it with the following:

                        "DEFAULT ON OTHER INDEBTEDNESS. (i) A default shall
            occur in the payment when due (subject to any applicable grace
            period), whether by acceleration or otherwise, of any Indebtedness
            of the Borrower or (ii) a default shall occur in the performance or
            observance of any obligation or condition with respect to such
            Indebtedness (other than the EME Revolvers) if the effect of such
            default is to accelerate the maturity of any such Indebtedness or
            such default shall continue unremedied for any applicable period of
            time sufficient to permit the holder or holders of such
            Indebtedness, or any trustee or agent for such holders, to cause
            such Indebtedness to become due and payable prior to its expressed
            maturity, in either case, such default having a principal amount,
            individually or in the aggregate, in excess of $20,000,000 (other
            than Indebtedness described in SECTION 8.1.1) or (iii) a default
            shall occur in the performance or observance of any obligation or
            condition with respect to any of the EME Revolvers (subject to any
            applicable grace period).".

            (m) SECTION 8.1.8 of the Credit Agreement shall be amended by
deleting Section 8.1.8 in its entirety and replacing it with the following:

            "[INTENTIONALLY OMITTED]".

            (n) ANNEX I of the Credit Agreement shall be deleted and replaced in
its entirety with Exhibit A hereto.

            Section 3. CONDITIONS PRECEDENT. This Amendment shall not become
effective until the date (the "AMENDMENT EFFECTIVE DATE") on which each of the
following conditions precedent have been satisfied or will be satisfied
contemporaneously with this Amendment becoming effective:

                  (a)  Delivery to the Administrative Agent of this Amendment
      duly executed and delivered by the Borrower, the Administrative Agent and
      each of the Lenders;

                  (b) The Administrative Agent shall have received opinions,
      dated the Amendment Effective Date and addressed to the Administrative
      Agent and the Lenders from (i) the in-house counsel to the Borrower and
      (ii) the special California counsel to the

                                 AMENDMENT TWO
<Page>

                                       9

      Borrower. Each such opinion shall be in form and substance reasonably
      satisfactory to the Administrative Agent;

                  (c) Delivery to the Administrative Agent of a certificate,
      executed by the controller, treasurer or chief financial officer of the
      Borrower, showing (in reasonable detail and with appropriate calculations
      and computations in all respects satisfactory to the Administrative Agent)
      compliance with the financial covenants set forth in SECTION 7.2.10 and
      SECTION 7.2.11 as of the Amendment Effective Date;

                  (d) The representations and warranties of the Borrower as set
      forth in the Credit Agreement shall be true and correct as of the
      Amendment Effective Date after giving effect to the amendments
      contemplated hereby (unless stated to be given as of an earlier date, in
      which case such representation and warranty shall be true and correct only
      as of such earlier date and except as set forth in the Borrower's Form
      10-K for the fiscal year ended December 31, 2000 and the Borrower's Form
      10-Q for the first quarter of 2001);

                  (e) As of the Amendment Effective Date, no Default shall have
      occurred and be continuing after giving effect to this Amendment;

                  (f) Amendment Three to the March Credit Agreement will become
      effective pursuant to the terms and conditions thereof contemporaneously
      with this Amendment; and

                  (g) Delivery to the Lenders of a Supplemental Agreement duly
      executed and delivered by the Borrower, the Administrative Agent and the
      other intended parties, substantially in the form heretofore furnished to
      the Lenders (and the Lenders hereby authorize the Administrative Agent to
      execute such Supplemental Agreement).

            Section 4. MISCELLANEOUS. Except as expressly amended hereby, all
of the terms and provisions of the Credit Agreement are and shall remain in
full force and effect. This Amendment may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument and any of the parties hereto may execute this Amendment by
signing any such counterpart. This Amendment shall be governed by, and
construed in accordance with, the law of the State of California.

                                 AMENDMENT TWO
<Page>

                                       S-1

            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed and delivered by their respective officers thereunto duly
authorized.

                                  EDISON MISSION ENERGY

                                  By: /s/  G. Gary Garcia
                                     ------------------------------------------
                                     Name:   G. Gary Garcia
                                     Title:  Treasurer

                                  BANK OF AMERICA, N.A.,
                                    as Administrative Agent and Lender

                                  By: /s/  Timothy C. Hintz
                                     ------------------------------------------
                                     Name: Timothy C. Hintz
                                     Title: Managing Director

                                  BARCLAYS BANK PLC

                                  By: /s/  Sydney G. Dennis
                                     ------------------------------------------
                                     Name: Sydney G. Dennis
                                     Title:  Director

                                  KBC BANK N.V.

                                  By: /s/ Jean-Pierre Diels /s/ Robert Snauffer
                                     ------------------------------------------
                                     Name:  Jean-Pierre Diels   Robert Snauffer
                                     Title: First Vice President     First Vice
                                                                      President

                                  TORONTO DOMINION (TEXAS) INC.

                                  By: /s/  Mark A. Baird
                                     ------------------------------------------
                                     Name:   Mark A. Baird
                                     Title:  Vice President

                                  AMENDMENT TWO
<Page>

                                      S-2

                                UNICREDITO ITALIANO

                                By: /s/ Gianfranco Bisagni /s/ Saiyed A. Abbas
                                   -------------------------------------------
                                   Name:  Gianfranco Bisagni   Saiyed A. Abbas
                                   Title: First Vice President  Vice President

                                WESTDEUTSCHE LANDESBANK GIROZENTRALE,
                                  NEW YORK BRANCH

                                By: /s/ Jasjeet S. Sood
                                   -------------------------------------------
                                   Name:   Jasjeet S. Sood
                                   Title:  Managing Director and
                                           Head of Energy Group

                                By: /s/ Jonathan Berman
                                   -------------------------------------------
                                   Name:   Jonathan Berman
                                   Title:  Managing Director

                                 AMENDMENT TWO

<Page>

                                                                       EXHIBIT A

                              EDISON MISSION ENERGY

                                   PRICING GRID

<Table>
<Caption>
=============================================================================================
                                        LEVEL 1                          LEVEL 2
BASIS FOR PRICING           LT Senior Unsecured Debt Rated   LT Senior Unsecured Debt Rated
                            At Least BBB By S&P AND  Baa2    Less Than Level 1 But At Least
                            By Moody's.                      BBB- By S&P AND Baa3 By Moody's.
=============================================================================================
<S>                         <C>                              <C>
APPLICABLE MARGIN (BASE                        50.00 bps                        75.00 bps
RATE LOANS)
---------------------------------------------------------------------------------------------
APPLICABLE MARGIN (LIBO                       150.00 bps                       287.50 bps
RATE LOANS)
=============================================================================================
FACILITY FEE (1)                               25.00 bps                        37.50 bps
---------------------------------------------------------------------------------------------
DRAWN COST  (2)             LIBOR    +        175.00 bps     LIBOR    +        325.00 bps
                            Base Rate +        75.00 bps     Base Rate +       112.50 bps
---------------------------------------------------------------------------------------------

<Caption>
==============================================================================================
                                         LEVEL 3                          LEVEL 4
BASIS FOR PRICING            LT Senior Unsecured Debt Rated   LT Senior Unsecured Debt Rated
                             Less Than Level 2 But At Least   Lower Than Level 3.
                             BB+ By S&P AND  Ba1 By Moody's.
==============================================================================================
<S>                          <C>                              <C>
APPLICABLE MARGIN (BASE                        100.00 bps                       150.00 bps
RATE LOANS)
----------------------------------------------------------------------------------------------
APPLICABLE MARGIN (LIBO                        325.00 bps                       400.00 bps
RATE LOANS)
==============================================================================================
FACILITY FEE (1)                                50.00 bps                        50.00 bps
----------------------------------------------------------------------------------------------
DRAWN COST  (2)              LIBOR    +        375.00 bps     LIBOR    +        450.00 bps
                             Base Rate +       150.00 bps     Base Rate +       200.00 bps
----------------------------------------------------------------------------------------------
</Table>

         (1)      Paid quarterly in arrears on each bank's commitment
                  irrespective of usage.
         (2)      Facility Fee plus Applicable Margin.

                  bps = basis points per annum

                                 AMENDMENT TWO<Page>

                                                                   Exhibit 10.91
                                                           EXECUTION COUNTERPART

                             SUPPLEMENTAL AGREEMENT

            SUPPLEMENTAL AGREEMENT (this "SUPPLEMENTAL AGREEMENT") dated as
of May 30, 2001 by and among EDISON MISSION ENERGY (the "BORROWER"), BANK OF
AMERICA, N.A. ("BOA"), as agent for the 425 Lenders (as defined below) and as
administrative agent for the 255 Lenders (as defined below) and CITICORP USA,
INC. ("CUSA") as administrative agent for the 595 Lenders (as defined below).

            WHEREAS, (a) the Borrower, certain of the lenders party thereto
(the "425 LENDERS") and BOA (formerly, the Bank of America National Trust and
Savings Association), as agent (the "425 AGENT") entered into the Second
Amended and Restated Credit Agreement dated as of October 11, 1996 (as
amended by Amendment One dated as of August 17, 2000 among the Borrower, the
425 Agent and the 425 Lenders party thereto, the "425 CREDIT AGREEMENT"); (b)
the Borrower, certain of the lenders party thereto (the "255 LENDERS") and
BOA as administrative agent (the "255 AGENT") entered into the Credit
Agreement dated as of May 30, 2000 (as amended by Amendment One dated as of
August 17, 2000 among the Borrower, the 255 Agent and the 255 Lenders party
thereto, the "255 CREDIT AGREEMENT"); and (c) the Borrower, certain of the
lenders party thereto (the "595 LENDERS", together with the 425 Lenders and
the 255 Lenders, the "LENDERS"), and CUSA as administrative agent (the "595
AGENT", together with the 425 Agent and the 255 Agent, the "AGENTS") entered
into a Credit Agreement dated as of March 18, 1999 (as amended by (i)
Amendment One dated as of August 17, 2000 among the Borrower, the 595 Agent
and the 595 Lenders party thereto and (ii) Amendment Two dated as of March
15, 2001 among the Borrower, the 595 Agent and the 595 Lenders party thereto,
the "595 CREDIT AGREEMENT"). The 425 Credit Agreement, the 255 Credit
Agreement and the 595 Credit Agreement as amended or modified from time to
time are herein referred to as the "CREDIT AGREEMENTS";

            WHEREAS, to induce the Lenders to enter into Amendment Two to the
425 Credit Agreement, Amendment Two to the 255 Credit Agreement and Amendment
Three to the 595 Credit Agreement, each dated as of the date hereof, the
Borrower has agreed to supplement each of the Credit Agreements as further
set forth in this Supplemental Agreement;

            ACCORDINGLY, the parties hereto agree as follows:

            Section 1. DEFINITIONS. Except as otherwise defined in this
Supplemental Agreement, terms defined in the Credit Agreements are used
herein (and in the introductions and recitals hereto) as defined therein.

            Section 2. LOAN DOCUMENT. The Borrower agrees that this
Supplemental Agreement shall be included in the definition of "LOAN DOCUMENT"
for the purposes of each of the Credit Agreements.

            Section 3. ADDITIONAL COVENANT. The Borrower shall not declare,
pay or make, or agree to declare, pay or make, either directly or indirectly,
Covered Distributions during the

<Page>

                                       2

period beginning on and including May 29, 2001 and ending on and including
October 10, 2001 in an aggregate amount exceeding $32,500,000. For the
purposes of this section, a "COVERED DISTRIBUTION" means (a) any dividend
(other than dividends payable solely in the common stock of the Borrower) on,
or any payment on account of, or any setting apart of assets for a sinking or
other analogous fund for, the purchase, redemption, defeasance, retirement or
other acquisition of, any shares of any class of capital stock of the
Borrower or any warrants or options to purchase any such stock, whether now
or hereafter outstanding, or any other distribution in respect thereof and
(b) any payment of the principal of, interest on or other amounts payable
with respect to intercompany loans to the Borrower from Edison International
or any subsidiary of Edison International that is not a subsidiary of the
Borrower.

            Section 4. ADDITIONAL EVENTS OF DEFAULT. The Borrower agrees that
the following events or occurrences shall constitute an "Event of Default"
under, and as defined in, each of the Credit Agreements:

            (a) The Borrower shall default in the performance and observance
of any of its obligations under Section 3 above; or

            (b) Any Change of Control shall occur. For purposes of this
section, "CHANGE OF CONTROL" means the failure of Edison International to
own, directly or indirectly, at least 50.1% of the outstanding shares of
voting stock of the Borrower (or any successor permitted pursuant to the
Credit Agreements) on a fully diluted basis.

            Section 5. PERIODS OF EFFECTIVENESS. The provisions of this
Supplemental Agreement shall be effective as to each Credit Agreement until
such Credit Agreement shall be fully and finally paid in full; PROVIDED that
the provisions of Sections 4(b) above shall cease to be effective as to each
Credit Agreement (and the events or occurrences set forth in Section 4(b)
above shall cease to be an Event of Default under each Credit Agreement) in
the event that (a) the Borrower shall have furnished to the Lenders a binding
financing commitment for a financing in an aggregate principal amount of at
least $275,000,000 that is in form and substance acceptable to the Requisite
COC Lenders from one or more banks or other financial institutions that are
acceptable to the Requisite COC Lenders the proceeds of which, when received
by the Borrower, shall be ratably applied to prepay permanently outstanding
loans under the Credit Agreements or (b) outstanding loans and commitments
under the Credit Agreements have been ratably reduced by at least
$275,000,000 by the application of the Net Cash Proceeds from the issuance or
incurrence by the Borrower of indebtedness. For purposes of this Supplemental
Agreement, "REQUISITE COC LENDERS" means (a) Required Lenders under, and as
defined in, each Credit Agreement AND (b) Lenders under the 595 Credit
Agreement that have no outstanding extensions of credit to Edison
International holding 85% of the aggregate outstanding principal amount of
the loans of such Lenders under the 595 Credit Agreement (or, if no such
loans are outstanding, 85% of the aggregate commitments of such Lenders under
the 595 Credit Agreement).

            Section 6. MODIFICATION. The provisions of this Supplemental
Agreement may only be amended, modified, waived or supplemented with the
prior written consent of (a) the Borrower, (b) the 425 Agent, acting at the
direction of the Requisite Lenders, (c) the 255 Agent, acting at the
direction of the Requisite Lenders and (d) the 595 Agent, acting at the
direction of

                               SUPPLEMENTAL AGREEMENT
<Page>

                                       3

the Requisite Lenders. For purposes of this Section, "REQUISITE LENDERS"
means, in the case of amendments, modifications, waivers or supplements to
(a) Section 3 or 4(a), Section 5 (as it may relate to Section 3 or 4(a)),
this Section 6(a) or any defined term used in said Sections, 100% of the
Lenders, (b) Section 4(b), Section 5 (as it may relate to Section 4(b)), this
Section 6(b) or any defined term used in said Sections, Requisite COC Lenders
and (c) any provision in this Supplemental Agreement not referred to in
clauses (a) or (b) above, Required Lenders under, and as defined in, each
Credit Agreement.

            Section 7. MISCELLANEOUS. This Supplemental Agreement may be
executed in any number of counterparts, all of which taken together shall
constitute one and the same instrument and any of the parties hereto may
execute this Supplemental Agreement by signing any such counterpart. This
Supplemental Agreement shall be governed by, and construed in accordance
with, the law of the State of New York.

                               SUPPLEMENTAL AGREEMENT
<Page>

                                      S-1

            IN WITNESS WHEREOF, the parties hereto have caused this
Supplemental Agreement to be executed and delivered by their respective
officers thereunto duly authorized.

                                    EDISON MISSION ENERGY

                                    By: /s/  G. Gary Garcia
                                       ---------------------------------------
                                       Name:  G. Gary Garcia
                                       Title: Treasurer

                                    BANK OF AMERICA, N.A.,
                                      as 425 Agent and as 255 Agent

                                    By: /s/ David Price
                                       ---------------------------------------
                                       Name:  David Price
                                       Title: Vice President

                                    CITICORP USA, INC.,
                                       as 595 Agent

                                    By: /s/  Anita J. Brickell
                                       ---------------------------------------
                                       Name:  Anita J. Brickell
                                       Title: Director

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