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                                                                    EXHIBIT 10.7

                                                                  EXECUTION COPY

                                 SIXTH AMENDMENT

                  SIXTH AMENDMENT, dated as of May 23, 2003 (this "Amendment"),
to the Second Amended and Restated Credit Agreement, dated as of May 23, 2000
(as amended, the "Credit Agreement"), among CALPINE CORPORATION, a Delaware
corporation (the "Borrower"), the various financial institutions as are or may
become parties thereto (the "Lenders") and THE BANK OF NOVA SCOTIA, as
administrative agent (in such capacity, the "Agent").

                  WHEREAS pursuant to the Credit Agreement, the Lenders have
made extensions of credit to the Borrower; and

                  WHEREAS the Borrower has requested that a provision of the
Credit Agreement be modified in the manner provided for in this Amendment, and
the Lenders are willing to agree to such modification as provided for in this
Amendment.

                  NOW, THEREFORE, the parties hereto hereby agree as follows:

                  1. Defined Terms. Capitalized terms used and not defined
herein shall have the meanings given to them in the Credit Agreement, as amended
hereby.

                  2. Amendment to Credit Agreement. The definition of
"Commitment Termination Date" in Section 1.1 of the Credit Agreement is hereby
amended by deleting clause (a) thereof in its entirety and by substituting in
lieu thereof the following: "(a) June 16, 2003;".

                  3. Representations and Warranties. The Borrower hereby
represents and warrants to the Agent and the Lenders that, as of the date hereof
and after giving effect to the amendment contained herein:

                  (a)      No Default or Event of Default has occurred and is
continuing.

                  (b)      The execution, delivery and performance by the
Borrower of this Amendment has been duly authorized by all necessary corporate
and other action and does not and will not require any registration with,
consent or approval of, notice to or action by, any person in order to be
effective and enforceable. Each of this Amendment and the Credit Agreement as
amended by this Amendment constitutes the legal, valid and binding obligation of
the Borrower, enforceable against each in accordance with its terms, subject to
applicable bankruptcy, insolvency, fraudulent conveyance, reorganization,
moratorium or other laws affecting creditors' rights generally and subject to
general principles of equity, regardless of whether considered in a proceeding
in equity or at law.

                  (c)      All representations and warranties of each Obligor
set forth in the Loan Documents as amended hereby are true and correct in all
material respects.

                  4. Covenants. The Borrower hereby agrees that during the
period commencing on the date hereof up to and including June 16, 2003 (the
"Extension Period"), the Borrower shall not take any action which could,
directly or indirectly, have a material adverse effect upon

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                                                                               2

(i) the financial condition, operations, assets (including power projects),
business or prospects of the Borrower and its Subsidiaries taken as a whole; or
(ii) the ability of the Borrower or any other Obligor to perform under any Loan
Document. Without prejudice to the foregoing, the Borrower shall ensure that,
during the Extension Period, (1) no Indebtedness is incurred, created, assumed
or suffered to exist by the Borrower or any of its Subsidiaries (except (A)
Indebtedness under the Loan Documents and the Loan Documents (as defined in the
2002 Credit Agreement), (B) unsecured Indebtedness incurred in the ordinary
course of business, other than Indebtedness of the type described in (1) clauses
(a), (c) or (f) of the definition of "Indebtedness" and (2) clauses (b) and (g)
of the definition of "Indebtedness" with respect to any Indebtedness described
in clause (1) above, (C) other unsecured Indebtedness or Non-Recourse Debt (as
defined in the Senior Note Indentures) incurred in the ordinary course of
business in connection with Indebtedness existing or contractually committed to
be made available as of the date hereof, and (D) Indebtedness outstanding on the
date hereof), and no guarantee, collateral or other credit support is provided,
and no Lien on the properties of the Borrower or any of its Subsidiaries is
created, incurred, assumed or granted, in each case in support of (x) any
Indebtedness (other than Indebtedness permitted above) or (y) any obligation
relating to any synthetic lease transaction of the Borrower or any Subsidiary of
the Borrower; (2) no amendment, modification or supplement is made to any
agreement or instrument evidencing any Indebtedness, other than amendments,
modifications or supplements entered into in the ordinary course of business in
respect of (A) the Credit Agreement or the 2002 Credit Agreement, (B) any
agreement or instrument evidencing Non-Recourse Debt (as defined in the Senior
Note Indentures) of a Subsidiary of the Borrower, or (C) any agreement or
instrument evidencing Indebtedness other than Indebtedness of the type described
in (1) clauses (a), (c) or (f) of the definition of "Indebtedness" and (2)
clauses (b) and (g) of the definition of "Indebtedness" with respect to any
Indebtedness described in clause (1) above (the Indebtedness described in
clauses (B) and (C) being collectively referred to as "Excluded Indebtedness");
(3) no optional prepayment is made on, or purchase or optional redemption is
executed of, any Indebtedness other than Excluded Indebtedness (including,
without limitation, any buy-back or defeasance of any outstanding bonds,
puttable convertible bonds or other securities of the Borrower or any of its
Subsidiaries), it being understood and agreed that, during the Extension Period,
neither the Borrower or any of its Subsidiaries shall obtain or receive any such
Indebtedness (or instruments evidencing same) in consideration of the sale or
other transfer of any assets or properties thereof; (4) no Investment is made by
the Borrower or any of its Subsidiaries in any other Person (except (A)
Investments by the Borrower in the ordinary course of business in Subsidiaries
the equity in which has been pledged to the Lenders, and each of their
respective Subsidiaries, (B) Investments by the Borrower in other Persons
pursuant to contractual commitments existing as of the date hereof, and (C)
Investments by the Borrower in CES in support of transactions entered into by
CES in the ordinary course of CES's business, consistent with historical
practices); and (5) all transactions between any one or more of the Borrower and
its Affiliates entered into during the Extension Period are on terms that are
fair and reasonable and similar to those found in a comparable arm's length
transaction with a Person that is not an Affiliate of the Borrower.
Notwithstanding the foregoing, it is agreed that (x) the Borrower and its
Subsidiaries may effectuate the transactions referred to in Schedule I attached
to the letter from the Borrower to the Lenders dated May 20, 2003 and (y) none
of the prohibitions contained in this Section 4 shall be applicable insofar as
they would otherwise constitute an encumbrance or restriction in violation of
Section 3.5 of the Pre-2000 Indentures (as defined in the 2002 Credit
Agreement). The provisions of this Section 4 may be amended,

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                                                                               3

modified or waived, if such amendment, modification or waiver is in writing and
consented to by the Borrower and Lenders owed or holding at least 51% of the
aggregate Revolving Loan Commitments and Commitments under the 2002 Credit
Agreement and the Credit Agreement, respectively (it being understood, however,
that no such amendment, modification or waiver shall amend, modify or waive the
provisions of the Credit Agreement unless such amendment, modification or waiver
satisfies the requirements of Section 11.1 of the Credit Agreement).

                  5. Conditions Precedent to Effectiveness. This Amendment shall
become effective as of the date hereof upon (i) the Agent having received
counterparts hereof duly executed and delivered by the Borrower and each Lender
and (ii) the Second Amendment, dated as of the date hereof, to the 2002 Credit
Agreement becoming effective in accordance with its terms.

                  6. No Other Amendments. Except as expressly amended hereby,
the provisions of the Credit Agreement are and shall remain in full force and
effect.

                  7. Expenses. The Borrower agrees to pay or reimburse the Agent
for its out-of-pocket expenses in connection with this Amendment, including the
reasonable fees, charges and disbursements of counsel to the Agent.

                  8. Governing Law; Counterparts. (a) This Amendment and the
rights and obligations of the parties hereto shall be governed by, and construed
and interpreted in accordance with, the laws of the State of New York.

                  (b)      This Amendment may be executed by one or more of the
parties to this Amendment on any number of separate counterparts, and all of
said counterparts taken together shall be deemed to constitute one and the same
instrument. This Amendment may be delivered by facsimile transmission of the
relevant signature pages hereof.

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                  IN WITNESS WHEREOF, the Borrower and the Lenders have caused
this Amendment to be duly executed by their respective authorized officers as of
the day and year first above written.

                                    CALPINE CORPORATION

                                    By   /s/ ROBERT D. KELLY
                                       -----------------------------------------
                                       Name: Robert D. Kelly
                                       Title: Chief Financial Officer

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                                    THE BANK OF NOVA SCOTIA, as Agent
                                    and Lender

                                    By   /s/ DENIS P. O'MEARA
                                       -----------------------------------------
                                       Name: Denis P. O'Meara
                                       Title: Managing Director

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                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    BAYERISCHE LANDESBANK
                                    CAYMAN ISLANDS BRANCH

                                    By   /s/ OLIVER HILDENBRAND
                                       -----------------------------------------
                                       Name: Oliver Hildenbrand
                                       Title: First Vice President

                                    By   /s/ JAMES H. BOYLE
                                       -----------------------------------------
                                       Name: James H. Boyle
                                       Title: Vice President

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    BANK OF AMERICA, NA

                                    By   /s/ EILEEN C. HIGGINS
                                       -----------------------------------------
                                       Name: Eileen C. Higgins
                                       Title: Principal

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    ING CAPITAL LLC

                                    By   /s/ ERWIN THOMET
                                       -----------------------------------------
                                       Name: Erwin Thomet
                                       Title: Managing Director

                                    By   /s/ NICK BELLAMY
                                       -----------------------------------------
                                       Name: Nick Bellamy
                                       Title: Director

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    CIBC INC.

                                    By   /s/ M. SANJEEVA SENANAYAKE
                                       -----------------------------------------
                                       Name: M. Sanjeeva Senanayake
                                       Title: Executive Director

                                           CIBC World Markets Corp. As Agent

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    DRESDNER BANK AG, NEW YORK
                                    and GRAND CAYMAN BRANCHES

                                    By   /s/ FRED THURSTON
                                       -----------------------------------------
                                       Name: Fred Thurston
                                       Title: Vice President

                                    By   /s/ THOMAS R. BRADY
                                       -----------------------------------------
                                       Name: Thomas R. Brady
                                       Title: Director

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    UNION BANK OF CALIFORNIA, N.A.

                                    By   /s/ BRYAN READ
                                       -----------------------------------------
                                       Name: Bryan Read
                                       Title: Vice President

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    BAYERISCHE HYPO-UND
                                    VEREINSBSBANK, AG, NY BRANCH

                                    By   /s/ PAUL J. COLATRELLA
                                       -----------------------------------------
                                       Name: Paul J. Colatrella
                                       Title: Director

                                    By   /s/ ANDREW G. MATHEWS
                                       -----------------------------------------
                                       Name: Andrew G. Mathews
                                       Title: Managing Director

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    FORTIS CAPITAL CORP.

                                    By   /s/ EDDIE MATTHEWS
                                       -----------------------------------------
                                       Name: Eddie Matthews
                                       Title: Senior Vice President

                                    By   /s/ MOHAMMED ALAM
                                       -----------------------------------------
                                       Name: Mohammed Alam
                                       Title: Vice President

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    CREDIT LYONNAIS NEW YORK BRANCH

                                    By   /s/ MARTIN C. LIVINGSTON
                                       -----------------------------------------
                                       Name: Martin C. Livingston
                                       Title: Vice President

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    FLEET NATIONAL BANK

                                    By   /s/ ANTHONY D. HEALEY
                                       -----------------------------------------
                                       Name: Anthony D. Healey
                                       Title: Authorized Signer

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    CREDIT SUISSE FIRST BOSTON

                                    By   /s/ JAMES P. MORAN
                                       -----------------------------------------
                                       Name: James P. Moran
                                       Title: Director

                                    By   /s/ BRIAN T. CALDWELL
                                       -----------------------------------------
                                       Name: Brian T. Caldwell
                                       Title: Director

<PAGE>

                                    Signature page to the Sixth Amendment, dated
                                    as of May 23, 2003, to the Second Amended
                                    and Restated Credit Agreement, dated as of
                                    May 23, 2000, as amended, among Calpine
                                    Corporation, the various financial
                                    institutions as are or may become parties
                                    thereto and The Bank of Nova Scotia, as
                                    administrative agent.

                                    TORONTO DOMINION (TEXAS) INC.

                                    By   /s/ DEBORAH GRAVINESE
                                       -----------------------------------------
                                       Name: Deborah Gravinese
                                       Title: Managing Director