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                                                                     Exhibit 4.9

                                                                  EXECUTION COPY



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                                    GUARANTEE


                           DATED AS OF AUGUST 17, 2000


                                   IN FAVOR OF


                                POWERTON TRUST I



                                     MADE BY


                              EDISON MISSION ENERGY,
                                  AS GUARANTOR

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                  GUARANTEE, dated as of August 17, 2000, (this "GUARANTEE")
made by EDISON MISSION ENERGY, a California corporation (the "GUARANTOR") in
favor of POWERTON TRUST I, a Delaware business trust and lessor under the
Facility Lease referred to below (the "OWNER LESSOR").


                               W I T N E S S E T H

                  WHEREAS, the Owner Lessor and Midwest Generation, LLC, a
Delaware limited liability company and lessee under the Facility Lease referred
to below (the "FACILITY LESSEE") are party to the Facility Lease (as from time
to time amended, supplemented, amended and restated or otherwise modified and in
effect from time to time, the "FACILITY LEASE") dated as of August 17, 2000
providing for the lease by the Owner Lessor to the Facility Lessee of an
undivided interest as tenant-in-common in the Facility. This Guarantee
guarantees the obligations of the Facility Lessee to pay Rent, including
Termination Value, owed to the Owner Lessor under the Facility Lease and the
other Operative Documents; and

                  WHEREAS, the Owner Lessor, Powerton Generation I, LLC,
Wilmington Trust Company, as the Owner Trustee, the Facility Lessee, the Guaran
tor, United States Trust Company of New York, as the Lease Indenture Trustee (as
such term is defined therein), United States Trust Company of New York, as the
Pass Through Trustees (as such term is defined therein) are party to the
Participation Agreement (as from time to time amended, supplemented, amended and
restated, or otherwise modified and in effect from time to time, the
"PARTICIPATION AGREEMENT") dated as of August 17, 2000 which establishes certain
rights and obligations of the parties to the leveraged lease financing of the
Powerton Station pursuant to the Facility Lease and the other Operative
Documents; and

                  WHEREAS, in connection with the Facility Lease, the Owner
Lessor and the Lease Indenture Trustee have entered into the Indenture of Trust,
Mortgage, and Security Agreement (as from time to time amended, supplemented,
amended and restated, or otherwise modified and in effect from time to time, the
"LEASE INDENTURE"), dated as of August 17, 2000 providing for the issuance by
the Owner Lessor of the notes (the "LESSOR NOTES").

                  WHEREAS, the Owner Lessor has granted to the Lease Indenture
Trustee for the benefit of the holders of the Lessor Notes a security interest
in the


                          POWERTON EME GUARTANTEE (T1)

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Trust Estate (as defined in the Lease Indenture and including, without
limitation, a collateral assignment of the Facility Lease and this Guarantee),
other than Excepted Payments (as defined in the Participation Agreement), as
security for the Lessor Notes and certain other obligations.

                  NOW, THEREFORE, for and in consideration of the premises and
mutual covenants herein contained, and for other good and valuable
consideration, the receipt and adequacy of which are hereby acknowledged, the
parties hereto, intending to be legally bound, do hereby covenant and agree as
follows:

                             ARTICLE 1. DEFINITIONS.

                  1.01 DEFINED TERMS. Each capitalized term used herein
(including in the preamble and recitals hereto) and not otherwise defined herein
shall have the definition assigned to that term in Appendix A to the
Participation Agreement.

                  1.02 INTERPRETATION. The rules of interpretation set forth in
Appendix A to the Participation Agreement shall apply MUTATIS MUTANDIS to this
Guarantee as if set forth in full in this SECTION 1.02.


                              ARTICLE 2. GUARANTEE.

                  2.01 THE GUARANTEE. The Guarantor hereby unconditionally and
irrevocably guarantees, as primary obligation and not merely as surety, to the
Owner Lessor and its successors and assigns the prompt payment in full when due
(whether at stated maturity, by acceleration or otherwise) of Rent, including
Termination Value, due to the Owner Lessor strictly in accordance with the terms
of the Facility Lease and the other Operative Documents; PROVIDED, that the
Guarantor's obligations hereunder shall not be subject to the limitation on
claims set forth in SECTION 18.19 of the Participation Agreement, SECTION 17.2
of the Facility Lease or the provisions of the Subordination Agreement (such
obligations being herein called the "GUARANTEED OBLIGATIONS"); PROVIDED,
FURTHER, that the Guaranteed Obligations constituting Termination Value may be
limited as set forth in Section 2.03 of this Guarantee. The Guarantor hereby
further agrees that if the Facility Lessee shall fail to pay in full when due
(whether at stated maturity, by acceleration or otherwise) any Guaranteed
Obligation payable by it, the Guarantor will promptly pay the same without
set-off or deduction and, without any demand or notice whatsoever, and that in
the case of any


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extension of time of payment or renewal of any Guaranteed Obligation, the same
will be promptly paid in full when due (whether at extended maturity, by
acceleration or otherwise) in accordance with the terms of such extension or
renewal.

                  2.02 OBLIGATIONS UNCONDITIONAL. The obligations of the
Guarantor under SECTION 2.01 are absolute and unconditional, irrespective of the
value, genuineness, validity, regularity or enforceability of the obligations
of the Facility Lessee under the Facility Lease or any other agreement or
instrument referred to therein, or any substitution, release or exchange of any
other guarantee of or security for the Guaranteed Obligations, and, to the
fullest extent permitted by applicable law, irrespective of any other
circumstance whatsoever that might otherwise constitute a legal or equitable
discharge or defense of a surety or guarantor, it being the intent of this
SECTION 2.02 that the obligations of the Guarantor hereunder shall be absolute
and unconditional, under any and all circumstances. Without limiting the
generality of the foregoing, it is agreed that the occurrence of any one or more
of the following shall not alter or impair the liability of the Guarantor
hereunder, which shall remain absolute and unconditional as described above:

         (i)      at any time or from time to time, without notice to the
                  Guarantor, the time for any performance of or compliance with
                  any of the Guaranteed Obligations shall be extended, or such
                  performance or compliance shall be waived;

         (ii)     any of the acts mentioned in any of the provisions of the
                  Operative Documents or any other agreement or instrument
                  referred to therein shall be done or omitted; or

         (iii)    the maturity of any of the Guaranteed Obligations shall be
                  accelerated, or any of the Guaranteed Obligations shall be
                  modified, supplemented or amended in any respect, or any
                  right under the Operative Documents or any other agreement or
                  instrument referred to therein shall be waived or any other
                  guarantee of a Guaranteed Obligation or any security therefor
                  shall be released or exchanged in whole or in part or
                  otherwise dealt with.

         Without limiting the generality of the foregoing, the Guarantor shall
have no right to terminate this Guarantee, or to be released, relieved or
discharged from its


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obligations hereunder, and such obligations shall be neither affected nor
diminished for any reason whatsoever, including:

         (i)      any amendment or supplement to or modification of any of the
                  Operative Documents, any extension or renewal of the Facility
                  Lessee's obligations under any Operative Document, or any
                  subletting, assignment or transfer of the Facility Lessee's
                  or the Owner Lessor's interest in the Operative Documents;

         (ii)     any bankruptcy, insolvency, readjustment, composition,
                  liquidation or any other change in the legal status of the
                  Facility Lessee or any rejection or modification of the
                  Guaranteed Obligations as a result of any bankruptcy,
                  reorganization, insolvency or similar proceeding;

         (iii)    any furnishing or acceptance of additional security or any
                  exchange, substitution, surrender or release of any security;

         (iv)     any waiver, consent or other action or inaction or any
                  exercise or nonexercise of any right, remedy or power with
                  respect to the Guaranteed Obligations or any of the Operative
                  Documents;

         (v)      the unenforceability, lack of genuineness or invalidity of the
                  Guaranteed Obligations or any part thereof or the
                  unenforceability, lack of genuineness or invalidity of any
                  agreement relating thereto;

         (vi)     (A) any merger or consolidation of the Facility Lessee or the
                  Guarantor into or with any other Person, (B) any change in
                  the structure of the Facility Lessee, (C) any change in the
                  ownership of the Facility Lessee or the Guarantor or (D) any
                  sale, lease or transfer of any or all of the assets of the
                  Facility Lessee or the Guarantor to any other Person;

         (vii)    any default, misrepresentation, negligence, misconduct or
                  other action or inaction of any kind by the Owner Lessor under
                  or in connection with any Operative Document or any other
                  agreement relating to this Guarantee, except to the extent
                  that any such default, misrepresentation, negligence,
                  misconduct or other action or inaction would limit the
                  Guaranteed Obligations;

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         (viii)   the subordination of any Guaranteed Obligation (or any portion
                  thereof) pursuant to Subordination Agreement or the exercise
                  of any right by any of the holders of any Senior Claims (as
                  defined in the Subordination Agreement) including any release,
                  discharge, compromise or settlement of any Guaranteed
                  Obligation (or any portion thereof); or

         (ix)     any other act, occurrence or circumstance whatsoever (except
                  the complete payment and performance of the Guaranteed
                  Obligations), including, without limitation, any act or
                  omission of the Facility Lessee or the Owner Lessor which
                  changes the scope of the Guarantor's risk.

         The Guarantor hereby expressly waives diligence, presentment, demand of
payment, protest and all notices whatsoever, and any requirement that the Owner
Lessor or any other Person exhaust any right, power or remedy or proceed against
the Facility Lessee under the Facility Lease, the other Operative Documents or
any other agreement or instrument referred to therein, or against any other
Person under any other guarantee of, or security for, the Guaranteed
Obligations.

                  2.03 GUARANTEED TV AMOUNT. If, during the period starting on
the date hereof and until the sixteenth anniversary of the Closing Date, upon a
Lease Event of Default, the Owner Lessor or the Lease Indenture Trustee, as the
case may be, exercises the remedies set forth in Sections 17.1(b), (c) and (d)
of the Facility Lease without first providing to the Facility Lessee and the
Guarantor a written demand for payment contemplated by Section 17.1(e) of the
Facility Lease (unless the Owner Lessor or the Lease Indenture Trustee, as the
case may be, is stayed or otherwise prevented by operation of law from issuing
such demand, in which event such written demand shall be deemed to have been
issued), then the obligations of the Guarantor under this Guarantee with respect
to payment of Termination Value shall be limited to the amount set forth on
Schedule 1 hereto applicable at such time.

                  2.04 REINSTATEMENT. The obligations of the Guarantor under
this Article 2 shall be automatically reinstated if and to the extent that for
any reason any payment by or on behalf of the Facility Lessee in respect of any
of the Guaranteed Obligations is rescinded or must be otherwise restored by any
holder of a Guaranteed Obligation, whether as a result of any proceedings in
bankruptcy or reorganization or


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otherwise, and the Guarantor agrees that it will indemnify the Owner Lessor on
demand for all reasonable costs and expenses (including fees of counsel)
incurred by the Owner Lessor in connection with such rescission or restoration,
including any such costs and expenses incurred in defending against any claim
alleging that such payment constituted a preference, fraudulent transfer or
similar payment under any bankruptcy, insolvency or similar law.

                  2.05 SUBROGATION. The Guarantor shall be subrogated to any and
all rights of the holders of the Guaranteed Obligations against the Facility
Lessee in respect of any amounts paid to the holders of the Guaranteed
Obligations in respect of any amounts paid by the Guarantor under this
Guarantee; PROVIDED, HOWEVER, that following the occurrence of a Specified Event
under and as defined in the EME Powerton (T1) Pledge Agreement the Guarantor
shall not be entitled to enforce or to exercise any rights that it may acquire
(or has theretofore acquired) by way of subrogation or any indemnity,
reimbursement or other agreement, in all cases as a result of performance by it
of its guarantee in SECTION 2.01 until such time as the Secured Obligations as
defined in the EME Powerton (T1) Pledge Agreement have been fully and
indefeasibly paid in full.

                  2.06 REMEDIES. The Guarantor agrees that, as between the
Guarantor, on the one hand and the Facility Lessee and the Owner Lessor, on the
other hand, the obligations of the Facility Lessee under the Facility Lease may
be declared to be forthwith due and payable as provided in SECTION 17 of the
Facility Lease (and shall be deemed to have become automatically due and payable
in the circumstances provided in said Section) for purposes of SECTION 2.01
notwithstanding any stay, injunction or other prohibition preventing such
declaration (or such obligations from becoming automatically due and payable) as
against the Facility Lessee and that, in the event of such declaration (or such
obligations being deemed to have become automatically due and payable), such
obligations (whether or not due and payable by Facility Lessee) shall forthwith
become due and payable by the Guarantor for purposes of SECTION 2.01.

                  2.07 INSTRUMENT FOR THE PAYMENT OF MONEY. The Guarantor hereby
acknowledges that the guarantee in this Article 2 constitutes an instrument for
the payment of money, and consents and agrees that the Owner Lessor, at its sole
option, in the event of a dispute by the Guarantor in the payment of any moneys
due hereunder, shall have the right to bring motion-action under New York CPLR
Section 3213.


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                  2.08 CONTINUING GUARANTEE.  This Guarantee is a continuing
guarantee, and shall apply to all of the Guaranteed Obligations whenever
arising.

                  2.09 PREPAYMENT UNDER INTERCOMPANY NOTE. The Guarantor
covenants that it will not elect to prepay the principal amount of the EME Note,
in whole or in part, prior to its stated maturity and it will not modify or
amend or permit the modification or amendment of, the EME Note without the prior
written consent of the Owner Lessor and the Owner Participant, which shall not
be unreasonably withheld.


                           ARTICLE 3. ASSIGNMENT, ETC.

                  3.01 PAYMENTS UNDER ASSIGNMENT. The Owner Lessor hereby
irrevocably directs (it being understood and agreed that such direction shall be
deemed to have been revoked after the Lien created under the Lease Indenture
shall have been fully discharged in accordance with its terms) the Guarantor,
and the Guarantor agrees, to make all payments pursuant to, and in the manner
set forth in, SECTION 2.01 hereof to the Lease Indenture Trustee's Account or
such other place as the Lease Indenture Trustee may notify the Guarantor in
writing pursuant to the Participation Agreement. The Guarantor hereby
acknowledges assignment of this Guarantee by the Owner Lessor to the Lease
Indenture Trustee for the benefit of the holders of the Lessor Notes. The
Guarantor agrees that the Lease Indenture Trustee (acting for the benefit of the
holders of the Lessor Notes) and any assignee thereof shall have the full right
and power to enforce directly against the Guarantor any and all obligations of
the Guarantor under this Guarantee and otherwise exercise all remedies hereunder
and to make any and all requests required or permitted to be made by the Owner
Trustee under this Guarantee.


                            ARTICLE 4. MISCELLANEOUS.

                  4.01 NO WAIVER. No failure on the part of the Owner Lessor or
the Guarantor to exercise and no delay in exercising, and no course of dealing
with respect to, any right, power or privilege hereunder shall operate as a
waiver thereof, and no single or partial exercise by the Owner Lessor or the
Guarantor of any right, power or privilege hereunder shall preclude any other or
further exercise thereof or



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the exercise of any other right, power or privilege. The remedies provided
herein are cumulative and are not exclusive of any remedies provided by
applicable law.

                  4.02 NOTICES. All notices, requests and other communications
provided for herein (including, without limitation, any modifications of, or
waivers under, this Guarantee) shall be given or made in writing (including,
without limitation, by telecopy) delivered to the intended recipient at the
"Address for Notices" specified below its name on the signature pages hereof,
or, as to any party, at such other address as shall be designated by such party
in a notice to each other party. Except as otherwise provided in this Guarantee,
all such communications shall be deemed to have been duly given (a) when
received by certified mail or by an international courier, such as Federal
Express, by such Person, at said address of such Person or (b) when transmitted
by facsimile to the number specified below and the receipt confirmed
telephonically by recipient, PROVIDED that such facsimile is promptly followed
by a copy of such notice delivered to such Person by postage-prepaid certified
mail, or by an international courier, such as Federal Express.

                  4.03 EXPENSES. The Guarantor agrees to pay to the Owner Lessor
all reasonable out-of-pocket expenses (including reasonable expenses for legal
services of every kind) of, or incident to, the enforcement of any of the
provisions of this Guarantee, and for the defending or asserting of rights and
claims of the Owner Lessor in respect thereof, by litigation or otherwise.

                  4.04 WAIVERS; ETC. The terms of this Guarantee may be waived,
altered or amended only by an instrument in writing duly executed by the Owner
Lessor and the Guarantor. Any such amendment or waiver shall be binding upon the
Owner Lessor, the Facility Lessee and the Guarantor.

                  4.05 SUCCESSORS AND ASSIGNS. This Guarantee shall be binding
upon and inure to the benefit of the respective successors and assigns of each
of the Owner Lessor and the Guarantor.

                  4.06 COUNTERPARTS; INTEGRATION: EFFECTIVENESS. This Guarantee
may be executed in any number of counterparts, all of which when taken together
shall constitute one and the same instrument, and any of the parties hereto may
execute this Guarantee by signing any such counterpart. This Guarantee
constitutes the entire agreement and understanding among the parties hereto and
supersedes any and all


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prior agreements and understandings, written or oral, relating to the subject
matter hereof.

                  4.07 SEVERABILITY. If any provision hereof is invalid or
unenforceable in any jurisdiction, then, to the fullest extent permitted by
applicable law, (a) the other provisions hereof shall remain in full force and
effect in such jurisdiction and shall be liberally construed in order to carry
out the intentions of the parties hereto as nearly as may be possible and (b)
the invalidity or unenforceability of any provision hereof in any jurisdiction
shall not affect the validity or enforceability of such provision in any other
jurisdiction.

                  4.08 HEADINGS. Headings appearing herein are used solely for
convenience of reference and are not intended to affect the interpretation of
any provision of this Guarantee.

                  4.09 SPECIAL EXCULPATION. NO CLAIM MAY BE MADE BY ANY PARTY
HERETO OR ANY OTHER PERSON AGAINST THE OTHER PARTY HERETO, THE OWNER LESSOR (OR
ANY PERSON FOR WHOSE BENEFIT THE OWNER LESSOR ACTS) OR THE AFFILIATES,
DIRECTORS, OFFICERS, EMPLOYEES, ATTORNEYS OR AGENTS OF ANY OF THEM FOR ANY
SPECIAL, INDIRECT, CONSEQUENTIAL OR PUNITIVE DAMAGES IN RESPECT OF ANY CLAIM
FOR BREACH OF CONTRACT OR ANY OTHER THEORY OF LIABILITY ARISING OUT OF OR
RELATING TO THIS GUARANTEE OR THE TRANSACTIONS CONTEMPLATED HEREBY, OR ANY ACT,
OMISSION OR EVENT OCCURRING IN CONNECTION THEREWITH AND EACH PARTY HERETO HEREBY
WAIVES, RELEASES AND AGREES, FOR ITSELF AND THOSE WHO CLAIM THROUGH IT, NOT TO
SUE UPON ANY CLAIM FOR ANY SUCH DAMAGES, WHETHER OR NOT ACCRUED AND WHETHER OR
NOT KNOWN OR SUSPECTED TO EXIST IN ITS FAVOR.

                  4.10 WAIVER OF JURY TRIAL. EACH OF THE OWNER LESSOR (FOR
ITSELF AND ON BEHALF OF EACH PERSON WHO CLAIMS THROUGH THE OWNER LESSOR) AND THE
GUARANTOR HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY
APPLICABLE LAW, ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING
ARISING OUT OF OR RELATING


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TO THIS GUARANTEE OR THE TRANSACTIONS CONTEMPLATED HEREBY.

                  4.11 NO THIRD PARTY BENEFICIARIES. THE AGREEMENTS OF THE
PARTIES HERETO ARE SOLELY FOR THE BENEFIT OF THE OWNER LESSOR (AND EACH PERSON
WHO CLAIMS THROUGH THE OWNER LESSOR), AND NO PERSON (OTHER THAN THE PARTIES
HERETO AND THEIR SUCCESSORS AND ASSIGNS PERMITTED HEREUNDER) SHALL HAVE ANY
RIGHTS HEREUNDER.

                  4.12 GOVERNING LAW; SUBMISSION TO JURISDICTION. This Guarantee
shall be governed by, and construed in accordance with, the law of the State of
New York. The Guarantor hereby submits to the non-exclusive jurisdiction of the
United States District Court for the Southern District of New York and of the
Supreme Court of the State of New York sitting in New York County (including its
Appellate Division) and of any other appellate court in the State of New York
for the purposes of all legal proceedings arising out of or relating to this
Guarantee or the transactions contemplated hereby. The Guarantor hereby
irrevocably waives, to the fullest extent permitted by applicable law, any
objection that it may now or hereafter have to the laying of the venue of any
such proceeding brought in such a court and any claim that any such proceeding
brought in such a court has been brought in an inconvenient forum.

                  4.13 LIMITATIONS OF LIABILITY OF TRUSTEE. It is expressly
understood and agreed by the parties hereto that this Guarantee is executed by
Wilmington Trust Company, not individually or personally, but solely as Trustee
under the Trust Agreement in the exercise of the power and authority conferred
and vested in it as such Trustee, that each and all of the representations,
undertakings and agreements herein made on the part of the Trustee or the Owner
Lessor are intended not as personal representations, undertakings and agreements
by Wilmington Trust Company, or for the purpose or with the intention of
binding Wilmington Trust Company, personally, but are made and intended for the
purpose of binding only the Trust Estate, that nothing herein contained shall be
construed as creating any liability of Wilmington Trust Company, or any
incorporator or any past, present or future subscriber to the capital stock of,
or stockholder, officer or director of Wilmington Trust Company, to perform any
covenant either express or implied contained herein or in the other Operative
Documents to which the Trustee or the Owner Lessor is a party, and that so far
as Wilmington Trust Company is concerned, any Person shall


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look solely to the Trust Estate for the performance of any obligation hereunder
or thereunder or under any of the instruments referred to herein or therein;
PROVIDED, that nothing contained in this SECTION shall be construed to limit in
scope or substance any general corporate liability of Wilmington Trust Company
as expressly provided in the Trust Agreement or in the Participation Agreement.


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                  IN WITNESS WHEREOF, the parties hereto have caused this
Guarantee to be duly executed and delivered as of the day and year first above
written.
                                       EDISON MISSION ENERGY,
                                       as Guarantor

                                       By:  /s/ John P. Finneran, Jr.
                                          --------------------------------------
                                           Name:    John P. Finneran, Jr.
                                           Title:   Vice President

                                       Address for Notices:

                                       18101 Von Karman Avenue
                                       Suite 1700
                                       Irvine, CA  92616
                                       Attention:
                                       Telecopier No.:

                                       POWERTON TRUST I, as Owner
                                       Lessor
                                          BY WILMINGTON TRUST
                                          COMPANY, not in its
                                          individual capacity
                                          but solely as trustee
                                          for Powerton Trust I

                                       By:  /s/  James P. Lawler
                                          --------------------------------------
                                           Name:    James P. Lawler
                                           Title:   Vice President

                                       Address for Notices:

                                       c/o Wilmington Trust Company
                                       Rodney Square North
                                       1100 North Market Street
                                       Wilmington, DE 19890
                                       Attention:   Corporate Trust
                                       Administration
                                       Telecopier No.:   (302) 651-8882



<PAGE>

                                                               Schedule 1 to the
                                                                    Powerton EME
                                                                       Guarantee

                              GUARANTEED TV AMOUNT