Exhibit 10.1

Execution Copy

CREDIT AGREEMENT

Dated as of February 23, 2005

among

Sigma-Aldrich Corporation,

The Lenders Party Hereto,

Wells Fargo Bank, National Association,

as Administrative Agent and

Letter of Credit Issuer

Wells Fargo Bank, National Association

and

Wachovia Capital Markets, LLC

as Joint Lead Arrangers

Wachovia Bank, N.A.,

as Syndication Agent

U.S. Bank N.A.

The Bank of Tokyo-Mitsubishi, Ltd., Chicago Branch

and

ABN AMRO Bank N.V.

as Co-Documentation Agents

i

ii

iii

Pricing Schedule – Revolving Facility

Pricing Schedule – Term Facility

Schedule 1.01 - Commitments

Schedule 4.05 - Litigation

Schedule 4.06 - ERISA

Schedule 4.09 - Subsidiaries

Schedule 5.07 - Existing Liens

Schedule 9.01 - Notice Information

Exhibit A-1 - Revolving Note

Exhibit A-2 - Term Note

Exhibit B - Opinion of Borrower’s Special Counsel

Exhibit C - Assignment and Assumption Agreement

Exhibit D - Compliance Certificate

Exhibit E - Form of Notice of Borrowing

Exhibit F - Form of Notice of Conversion/Continuation

Exhibit G - Form of Lender Assumption Agreement

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CREDIT AGREEMENT

THIS CREDIT AGREEMENT, dated as of February 23, 2005, is by and among SIGMA-ALDRICH CORPORATION, a Delaware corporation, the Lenders from time to time party hereto, WELLS FARGO BANK, NATIONAL ASSOCIATION, as Administrative Agent and Letter of Credit Issuer, WELLS FARGO BANK, NATIONAL ASSOCIATION and WACHOVIA CAPITAL MARKETS, LLC as Joint Lead Arrangers for the Lenders, WACHOVIA BANK, N.A., as Syndication Agent, and ABN AMRO BANK N.V., THE BANK OF TOKYO-MITSUBISHI, LTD., CHICAGO BRANCH AND U.S. BANK N.A., as Co-Documentation Agents.

W I T N E S S E T H:

WHEREAS, the Borrower has requested that the Lenders provide a credit facility to the Borrower in an aggregate principal amount not to exceed $300,000,000 at any time outstanding, consisting of (i) a revolving credit facility to the Borrower in an aggregate principal amount not to exceed $150,000,000 at any time outstanding (except as provided in Section 2.08(c)); and (ii) a term loan facility to the Borrower in an aggregate principal amount not to exceed $150,000,000 at any time outstanding;

WHEREAS, the proceeds of (i) the revolving credit facility will be used by the Borrower for general corporate purposes, including, without limitation, to pay commercial paper obligations of the Borrower and issue Letters of Credit, and (ii) the term loan facility will be used by the Borrower to fund a portion of the purchase price for the acquisition of JRH Biosciences, a division of CSL Limited, a company incorporated in England and Wales (“JRH/UK”), JRH Biosciences PTY Ltd., a company incorporated in Australia (“JRH/Australia”), CSL US Inc., a Delaware corporation (“JRH/US”, each a direct or indirect susidiary of CSL Limited, a company incorporated in Australia and collectively “JRH Biosciences”); and

WHEREAS, the Lenders are willing to extend Commitments to make Loans and issue Letters of Credit to the Borrower hereunder, in each case, for the respective purposes provided herein and only on the terms and subject to the conditions hereinafter set forth.

NOW, THEREFORE, in consideration of the premises and of the mutual covenants herein contained, the parties hereto agree as follows:

ARTICLE I

DEFINITIONS

Section 1.01 Definitions. The following terms, as used herein, have the following meanings:

“Administrative Agent” means Wells Fargo in its capacity as Administrative Agent for the Lenders hereunder, and its successors in such capacity.

“Administrative Agent-Related Persons” means the Administrative Agent (including any successor Administrative Agent), together with its Affiliates, and the officers, directors, employees, agents and attorneys-in-fact of such Persons and Affiliates.

“Administrative Questionnaire” means, with respect to each Lender, an administrative questionnaire in the form prepared by the Administrative Agent and submitted to the Administrative Agent duly completed by such Lender.

“Affiliate” means, with respect to any Person, any other Person that directly, or indirectly through one or more intermediaries, controls, is controlled by or is under common control with such Person. As used herein, the term “control” means possession, directly or indirectly, of the power to direct or cause the direction of the management or policies of a Person, whether through the ownership of voting securities, by contract or otherwise; provided that any Person which does not own, directly or indirectly, more than 15% of any class of voting securities (or other ownership interests) of such other Person shall not be deemed to “control” such Person.

“Agreement” means this Credit Agreement, as amended, supplemented or otherwise modified from time to time.

“Applicable Lending Office” means, with respect to any Lender, (i) in the case of its Base Rate Loans, its Base Rate Lending Office and (ii) in the case of its LIBOR Loans, its LIBOR Lending office.

“Assignee” has the meaning set forth in Section 9.06(c).

“Assignment and Assumption Agreement” has the meaning set forth in Section 9.06(c).

“Authorized Officer” means any of the Chairman, Chief Executive Officer, President, Chief Operating Officer, Chief Financial Officer, Treasurer, Corporate Controller or any Vice President and Chief Administrative Officer of the Borrower or any other officer designated by the Borrower in writing to the Administrative Agent, in each case acting singly.

“Bankruptcy Code” means chapter 11 of title 11 of the United States Code, 11 U.S.C. §101 et. seq.

“Base Rate” means, for any day, a rate of interest per annum equal to the higher of (i) the Prime Rate for such day, and (ii) the sum of the Federal Funds Effective Rate for such day plus 1/2% per annum.

“Base Rate Lending Office” means, as to each Lender, its office located at its address set forth in its Administrative Questionnaire (or identified in its Administrative Questionnaire as its Base Rate Lending Office) or such other office as such Lender may hereafter designate as its Base Rate Lending Office by notice to the Borrower and the Administrative Agent.

“Base Rate Loan” means a Loan bearing interest at the Base Rate.

“Benefit Arrangement” means at any time an employee benefit plan within the meaning of Section 3(3) of ERISA which is not a Plan or a Multiemployer Plan and which is maintained or otherwise contributed to by any member of the ERISA Group.

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“Board of Directors” means the board of directors of the Borrower as it may be constituted at any relevant time.

“Borrower” means Sigma-Aldrich Corporation, a Delaware corporation, and its successors.

“Borrowing” has the meaning set forth in Section 1.03.

“Business Day” means (i) with respect to any borrowing, payment or rate selection of LIBOR Loans a day (other than a Saturday on Sunday) on which banks generally are open in Chicago and San Francisco for the conduct of substantially all of their commercial lending activities and on which dealings in United States dollars are carried on in the London interbank market and (ii) for all other purposes, a day (other than a Saturday or Sunday) on which banks generally are open in Chicago and San Francisco for the conduct of substantially all of their commercial lending activities.

“Capital Lease Obligation” of any Person means the obligation to pay rent or other payment amounts under a lease of (or other indebtedness arrangements conveying the right to use) real or personal property of such Person which is required to be classified and accounted for as an asset and a liability on the face of a balance sheet of such Person in accordance with generally accepted accounting principles.

“Capitalization Ratio” means at any date the ratio of (x) Consolidated Debt, to (y) the sum of Consolidated Debt plus Consolidated Net Worth.

“Commitment” means, with respect to any Lender, the aggregate amount of its Total Revolving Commitments and Term Commitments.

“Commitment Percentage” means, with respect to each Lender, the percentage equal to a fraction the numerator of which is the amount of such Lender’s Commitment and the denominator of which is the aggregate amount of the Commitments of the Lenders.

“Compliance Certificate” means a certificate delivered in accordance with Section 5.01(c).

“Consolidated Debt” means at any date the Debt of the Borrower and its Subsidiaries, determined on a consolidated basis as of such date.

“Consolidated Net Worth” means, at any time: (a) the total assets of the Borrower and its Subsidiaries which would be shown as assets on a consolidated balance sheet of the Borrower and its Subsidiaries as of such time prepared in accordance with generally accepted accounting principles, after eliminating all amounts properly attributable to minority interests, if any, in the stock and surplus of Subsidiaries; minus (b) the total liabilities of the Borrower and its

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Subsidiaries which would be shown as liabilities on a consolidated balance sheet of the Borrower and its Subsidiaries as of such time prepared in accordance with generally accepted accounting principles; minus (c) any consolidated balance sheet foreign currency translation adjustment.

“Debt” of any Person means at any date, without duplication, (i) all obligations of such Person for borrowed money, (ii) all obligations of such Person evidenced by bonds, debentures, notes or other similar instruments, (iii) all fixed or contingent reimbursement obligations of such Person with respect to letters of credit, (iv) all obligations of such Person to pay the deferred purchase price of property or services (other than trade accounts payable, deferred compensation items, and like expense accruals arising in the ordinary course of business), except, in the case of property, to the extent that the rights and remedies of the obligor with respect to such obligations are limited to repossession or sale of such property, (v) all Capital Lease Obligations of such Person, (vi) all obligations of such Person for Swaps, (vii) all Debt of others secured by a Lien on any asset of such Person, whether or not such Debt is assumed by such Person, (viii) the aggregate amount of uncollected accounts receivable of such Person subject at such time to a sale of receivables (or similar transaction) regardless of whether such transaction is effected without recourse to such Person or in a manner that would not be reflected on the balance sheet of such Person in accordance with generally accepted accounting principles, (ix) all Synthetic Lease Obligations, and (x) all Debt of others Guaranteed by such Person. The amount of any Debt secured by a Lien pursuant to clause (vii) above shall be an amount equal to the lesser of (x) the aggregate outstanding amount of Debt secured by such Lien and (y) the greater of the aggregate book value and the aggregate fair market value of the assets subject to such Lien.

“Default” means any condition or event which constitutes an Event of Default or which with the giving of notice or lapse of time, or both, would, unless cured or waived, become an Event of Default.

“Effective Date” means the date this Agreement becomes effective in accordance with Section 3.01.

“Environmental Laws” means any and all federal, state, local and foreign statutes, laws, regulations, ordinances, rules or other governmental restrictions relating to the environment or to emissions, discharges or releases of pollutants, contaminants, petroleum or petroleum products, chemicals or toxic or hazardous substances or wastes into the environment including, without limitation, ambient air, surface water, ground water, or land, or otherwise relating to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of pollutants, contaminants, petroleum or petroleum products, chemicals or toxic or hazardous substances or wastes or the clean-up or other remediation thereof and any and all judgments, orders, decrees, permits, grants, franchises, licenses or agreements relating to the foregoing to which the Borrower or any Subsidiary is a party or which is otherwise applicable to the Borrower or any Subsidiary.

“Eligible Lender” means a financial institution mutually agreed upon by both Administrative Agent and Borrower, such consent shall not be unreasonably withheld.

“ERISA” means the Employee Retirement Income Security Act of 1974, as amended, or any successor statute.

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“ERISA Group” means the Borrower and all members of a controlled group of corporations and all trades or businesses (whether or not incorporated) under common control which, together with the Borrower, are treated, on or after the Effective Date, as a single employer under Section 414 of the Internal Revenue Code.

“Event of Default” has the meaning set forth in Section 6.01.

“Existing 364-Day Agreement” means that certain Credit Agreement (364-Day Facility) dated as December 12, 2001 among the Borrower, the Lenders party thereto, Wells Fargo Bank, National Association, as Administrative Agent and as sole Lead Arranger, Wachovia Bank, N.A. and U.S. Bank N.A., as Co-Syndication Agents, and ABN AMRO Bank N.V. and The Bank of Tokyo-Mitsubishi, Ltd., Chicago Branch, as Co-Documentation Agents, as from time to time amended, restated or modified.

“Facility Fee Rate” has the meaning set forth in Section 2.07(a).

“Federal Funds Effective Rate” means, for any day, an interest rate per annum equal to the weighted average of the rates on overnight Federal funds transactions with members of the Federal Reserve System arranged by Federal funds brokers on such day, as published for such day (or, if such day is not a Business Day, for the immediately preceding Business Day) by the Federal Reserve Bank of New York, or, if such rate is not so published for any day which is a Business Day, the average of the quotations at approximately 9:00 a.m. (Chicago time) on such day on such transactions received by the Administrative Agent from three Federal funds brokers of recognized standing selected by the Administrative Agent in its sole discretion.

“Fee Letter” means either of the letter agreements, relating to certain agency and arrangement fees, between the Borrower and (i) Wells Fargo, in its capacity as Administrative Agent and Joint Lead Arranger, or (ii) Wachovia Bank, N.A. in its capacity as Joint Lead Arranger, as amended, supplemented or otherwise modified from time to time.

“Fiscal Quarter” means a fiscal quarter of the Borrower.

“Fiscal Year” means a fiscal year of the Borrower.

“5-Year Agreement” means that certain Credit Agreement (5-Year Facility) dated as of December 12, 2001 among the Borrower, the Lenders party thereto, Wells Fargo Bank, National Association, as Administrative Agent and as sole Lead Arranger, Wachovia Bank, N.A. and U.S. Bank N.A., as Co-Syndication Agents, and ABN AMRO Bank N.V. and The Bank of Tokyo-Mitsubishi, Ltd., Chicago Branch, as Co-Documentation Agents, as from time to time amended, restated or modified.

“Governmental Authority” shall mean any nation or government where the Borrower or its Subsidiaries do business, any state or other political subdivision thereof, any central bank (or similar monetary or regulatory authority) thereof, any entity exercising executive, legislative,

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judicial, regulatory or administrative functions of or pertaining to government, and any corporation or other entity owned or controlled, through stock or capital ownership or otherwise, by any of the foregoing.

“Guarantee” by any Person means any obligation, contingent or otherwise, of such Person directly or indirectly guaranteeing any Debt of any other Person and, without limiting the generality of the foregoing, any obligation, direct or indirect, contingent or otherwise, of such Person (i) to purchase or pay (or advance or supply funds for the purchase or payment of) such Debt or other obligation (whether arising by virtue of partnership arrangements, by agreement to keep-well, to purchase assets, goods, securities or services, to take-or-pay, or to maintain financial statement conditions or otherwise) or (ii) entered into for the purpose of assuring in any other manner the obligee of such Debt of the payment thereof or to protect such obligee against loss in respect thereof (in whole or in part); provided that the term “Guarantee” shall not include endorsements for collection or deposit in the ordinary course of business. The term “Guarantee” used as a verb has a corresponding meaning.

“Interest Period” means, with respect to each LIBOR Loan, the period commencing on the date of such Borrowing and ending 1, 2, 3, 6, 9 or 12 months thereafter, as the Borrower may elect in the applicable Notice of Borrowing; provided that:

“Internal Revenue Code” means the Internal Revenue Code of 1986, as amended, or any successor statute.

“Investment” means any investment in any Person, whether by means of share purchase, capital contribution, loan, time deposit or otherwise.

“Issuance Request” shall have the meaning set forth in Section 2.15.4.

“JRH Biosciences” means JRH Biosciences Limited, a company incorporated in England and Wales, JRH Biosciences Pty Ltd., a company incorporated in Australia, CSL US Inc., a Delaware corporation, and JRH Biosciences, Inc., a Delaware corporation.

“Lender” means each lender listed on the signature pages hereof, each Assignee which becomes a Lender pursuant to Section 9.06(c), and their respective successors and assigns.

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“Lending Office” means the LIBOR Lending Office or Base Rate Lending Office, as applicable.

“Letter of Credit” means a Letter of Credit issued pursuant to Section 2.15.

“Letter of Credit Expiry Date” means, with respect to any Letter of Credit, the date which is one (1) year after the date of issuance therefor.

“Letter of Credit Issuer” means Wells Fargo, as issuer of the Letters of Credit.

“Letter of Credit Issuer-Related Persons” means the Letter of Credit Issuer (including any successor Administrative Agent), together with its Affiliates, and the officers, directors, employees, agents and attorneys-in-fact of such Persons and Affiliates.

“Letter of Credit Obligations” means, as at the time of determination thereof, the sum of (a) the Reimbursement Obligations then outstanding, and (b) the aggregate undrawn face amount of the then outstanding Letters of Credit.

“Letter of Credit Sublimit” means an aggregate amount of $50,000,000.

“LIBOR Base Rate” means, with respect to LIBOR Loans for the relevant Interest Period, the rate determined by the Administrative Agent to be the rate at which Wells Fargo offers to place deposits in U.S. dollars with first-class banks in the London interbank market at approximately 11:00 a.m. (London time) two Business Days prior to the first day of such Interest Period, in the approximate amount of Wells Fargo’s relevant LIBOR Loan and having a maturity equal to such Interest Period.

“LIBOR Lending Office” means, as to each Lender, its office, branch or affiliate located at its address set forth in its Administrative Questionnaire (or identified in its Administrative Questionnaire as its LIBOR Lending Office) or such other office, branch or affiliate of such Lender as it may hereafter designate as its LIBOR Lending Office by notice to the Borrower and the Administrative Agent.

“LIBOR Loan” means a Loan bearing interest at the LIBOR Rate.

“LIBOR Margin” means, with respect to LIBOR Loans at any time, the percentage rate per annum which is applicable at such time with respect to LIBOR Loans as set forth in the Pricing Schedule.

“LIBOR Rate” means, with respect to LIBOR Loans for the relevant Interest Period, the sum of (i) the quotient of (a) the LIBOR Base Rate applicable to such Interest Period, divided by (b) one minus the Reserve Requirement (expressed as a decimal) applicable to such Interest Period, plus (ii) the LIBOR Margin. The LIBOR Rate shall be rounded to the next higher multiple of 1/16 of 1% if the rate is not such a multiple.

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“Lien” means, with respect to any asset, any mortgage, lien, pledge, security interest or encumbrance of any kind in respect of such asset, including any conditional sale or other title retention agreement.

“Loan” means a Revolving Loan or Term Loan, as the case may be.

“Loan Document” means this Agreement, the Fee Letters and any Notes issued hereunder.

“Material Adverse Effect” means a material adverse effect on: (i) the business, operations, affairs, financial condition, assets or properties of the Borrower and its Subsidiaries taken as a whole; (ii) the ability of the Borrower to perform its obligations under the Loan Documents; or (iii) the legality, validity or enforceability of the Loan Documents.

“Material Debt” means Debt (other than the Notes) of the Borrower and/or one or more of its Subsidiaries, arising in one or more related or unrelated transactions, in an aggregate principal amount exceeding $30,000,000.

“Material Plan” means at any time a Plan or Plans having aggregate Unfunded Liabilities in excess of $10,000,000.

“Moody’s” means Moody’s Investors Service, Inc. or any successor thereto.

“Multiemployer Plan” means at any time an employee pension benefit plan within the meaning of Section 4001(a) (3) of ERISA to which any member of the ERISA Group is then making or accruing an obligation to make contributions or has within the preceding five plan years made contributions, including for these purposes any Person which ceased to be a member of the ERISA Group during such five-year period.

“Notes” means the Revolving Notes and the Term Notes, and “Note” means any of the Revolving Notes or Term Notes.

“Notice of Borrowing” means a Notice of Borrowing (as defined in Section 2.02(a)) executed by a Senior Financial Officer.

“OFAC” means the United States Department of the Treasury’s Office of Foreign Assets Control.

“Obligations” means all unpaid principal of and accrued and unpaid interest on the Loans, all Letter of Credit Obligations, and all accrued and unpaid fees, expenses, reimbursements, indemnities and other obligations of the Borrower to the Lenders or to any Lender, the Administrative Agent or any indemnified party arising under the Loan Documents.

“Parent” means, with respect to any Lender, any Person controlling (as defined under the definition of “Affiliate” herein) such Lender.

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“Participant” has the meaning set forth in Section 9.06(b).

“Payment Office” means the main office of the Administrative Agent located in San Francisco, California.

“PBGC” means the Pension Benefit Guaranty Corporation or any entity succeeding to any or all of its functions under ERISA.

“Permitted Disposition” has the meaning set forth in Section 5.08(c).

“Person” means an individual, a corporation, a partnership, a limited liability company, an association, a trust or any other entity or organization, including a government or political subdivision or an agency or instrumentality thereof.

“Plan” means at any time an employee pension benefit plan (other than a Multiemployer Plan) which is covered by Title IV of ERISA or subject to the minimum funding standards under Section 412 of the Internal Revenue Code and either (i) is maintained, or contributed to, by any member of the ERISA Group for employees of any member of the ERISA Group or (ii) has at any time within the preceding five years been maintained, or contributed to, by any Person which was at such time a member of the ERISA Group for employees of any Person which was at such time a member of the ERISA Group.

“Pricing Schedule” means the Pricing Schedule attached hereto.

“Prime Rate” means at any time the rate of interest per annum most recently announced within Wells Fargo at its principal office in San Francisco, California as its Prime Rate, with the understanding that Wells Fargo’s Prime Rate is one of its base rates and serves as the basis upon which effective rates of interest are calculated for those loans making reference thereto and is evidenced by the recording thereof after its announcement in such internal publication or publications as Wells Fargo may designate. Each change in the Prime Rate shall be effective on the day the change is announced within Wells Fargo.

“Register” has the meaning set forth in Section 9.06(f).

“Regulation D” means Regulation D of the Board of Governors of the Federal Reserve System as from time to time in effect and any successor thereto or other regulation or official interpretation of said Board of Governors relating to reserve requirements applicable to member banks of the Federal Reserve System.

“Regulation U” means Regulation U of the Board of Governors of the Federal Reserve System, as in effect from time to time and any successor thereto or other regulation or official interpretation of said Board of Governors relating to the extension of credit by banks for the purpose of purchasing or carrying margin stocks applicable to member banks of the Federal Reserve System.

“Reimbursement Agreement” means a letter of credit application and reimbursement

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agreement in such form as the Letter of Credit Issuer may from time to time employ in the ordinary course of business. In the event of any inconsistency between the Agreement and any Reimbursement Agreement, this Agreement shall govern.

“Reimbursement Obligations” means, at any time, the aggregate (without duplication) of the Obligations of the Borrower to the Lenders, the Letter of Credit Issuer and/or the Administrative Agent in respect of all unreimbursed payments or disbursements made by the Lenders, the Letter of Credit Issuer and/or the Administrative Agent under or in respect of draws made under the Letters of Credit.

“Required Lenders” means at any time Lenders having at least (i) 51% of the aggregate amount of the Commitments, and (ii) to the extent any Commitments have terminated, then 51% of the aggregate unpaid principal amount of Notes outstanding under such terminated Commitments.

“Reserve Requirement” means, with respect to an Interest Period, the maximum, aggregate reserve requirement (including all basic, supplemental, marginal and other reserves) which is imposed under Regulation D on eurocurrency liabilities.

“Revolving Commitment” means, with respect to any Lender, the principal amount set forth opposite the name of such Lender on Schedule 1.01 hereto or in any Assignment and Assumption Agreement under the caption “Amount of Revolving Commitment”, and “Revolving Commitments” means such commitments collectively, which commitments equal $150,000,000 in the aggregate as of the Effective Date, as such amount may be changed from time to time pursuant to Section 2.08.

“Revolving Commitment Percentage” means, with respect to each Lender, the percentage equal to a fraction the numerator of which is the amount of such Lender’s Revolving Commitment and the denominator of which is the aggregate amount of the Revolving Commitments of the Lenders.

“Revolving Loan” means a loan made by a Lender pursuant to Section 2.01 (a), which may be a Base Rate Loan or a LIBOR Loan.

“Revolving Loan Availability Period” means the period from and including the Effective Date to but not including the Revolving Loan Termination Date.

“Revolving Loan Termination Date” means February 23, 2010.

“Revolving Note” means promissory notes of the Borrower, substantially in the form of Exhibit A-1 hereto, evidencing the obligation of the Borrower to repay the Revolving Loans, and “Revolving Note” means any one of such promissory notes issued hereunder, as the same may be amended, supplemented or otherwise modified from time to time.

“Sale and Leaseback Transaction” of any Person means an arrangement with any lender or investor or to which such lender or investor is a party providing for the leasing by such Person

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of any property that has been or is being sold, conveyed, transferred or otherwise disposed of by such Person to such lender or investor or to any Person to whom funds have been or are to be advanced by such lender or investor on the security of such property.

“S&P” means Standard & Poor’s Ratings Group, a division of The McGraw-Hill Companies, Inc., and any successor thereto.

“Securities Exchange Act” means the Securities Exchange Act of 1934, as amended.

“Senior Financial Officer” means the chief financial officer, principal accounting officer, treasurer or controller of the Borrower.

“Subsidiary” of a Person means any corporation, association, partnership, limited liability company, joint venture or other business entity of which more than 50% of the voting stock, membership interests or other equity interests (in the case of Persons other than corporations), is owned or controlled directly or indirectly by the Person, or one or more of the Subsidiaries of the Person, or a combination thereof. Unless the context otherwise clearly requires, references herein to a “Subsidiary” refer to a Subsidiary of the Borrower or one of the Subsidiaries.

“Swaps” means, with respect to any Person, payment obligations with respect to interest rate swaps, currency swaps and similar obligations (other than forward currency contracts) obligating such Person to make payments, whether periodically or upon the happening of a contingency. For the purposes of this Agreement, the amount of the obligation under any Swap shall be the amount determined in respect thereof as of the end of the then most recently ended fiscal quarter of such Person, based on the assumption that such Swap had terminated at the end of such fiscal quarter, and in making such determination, if any agreement relating to such Swap provides for the netting of amounts payable by and to such Person thereunder or if any such agreement provides for the simultaneous payment of amounts by and to such Person, then and in each such case, the amount of such obligations shall be the net amount so determined.

“Synthetic Lease Obligation” of any Person means the obligation to pay rent or other payment amounts under a lease of (or other indebtedness arrangements conveying the right to use) real or personal property of such Person which may be classified and accounted for as an operating lease or off-balance sheet liability for accounting purposes but as a secured or unsecured loan for tax purposes under the Internal Revenue Code.

“Term Commitment” means, with respect to any Lender, the principal amount set forth opposite the name of such Lender on Schedule 1.01 hereto or in any Assignment and Assumption Agreement under the caption “Amount of Term Commitment”, and “Term Commitments” means such commitments collectively, which commitments equal $150,000,000 in the aggregate as of the Effective Date, as such amount may be changed from time to time pursuant to Section 2.08.

“Term Commitment Percentage” means, with respect to each Lender, the percentage equal to a fraction the numerator of which is the amount of such Lender’s Term Commitment and the denominator of which is the aggregate amount of the Term Commitments of the Lenders.

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“Term Loan” means a loan made by a Lender pursuant to Section 2.01 (b), which may be a Base Rate Loan or a LIBOR Loan.

“Term Loan Availability Period” means the period from and including the Effective Date to but not including June 1, 2005.

“Term Loan Termination Date” means February 23, 2008.

“Term Note” means promissory notes of the Borrower, substantially in the form of Exhibit A-2 hereto, evidencing the obligation of the Borrower to repay the Term Loans, and “Term Note” means any one of such promissory notes issued hereunder, as the same may be amended, supplemented or otherwise modified from time to time.

“Total Revolving Commitment” means, with respect to any Lender, its Revolving Commitment under this Agreement plus its commitment pursuant to the 5-Year Agreement, and “Total Revolving Commitments” means such commitments collectively for all Lenders, which commitments equal $300,000,000 in the aggregate as of the Effective Date, as such amount may be changed from time to time pursuant to Section 2.08 hereof or Section 2.08 of the 5-Year Agreement.

“Unfunded Liabilities” means, with respect to any Plan at any time, the amount (if any) by which (i) the present value of all benefits under such Plan exceeds (ii) the fair market value of all Plan assets allocable to such benefits (excluding any accrued but unpaid contributions), all determined as of the then most recent valuation date for such Plan, but only to the extent that such excess represents a potential liability of a member of the ERISA Group to the PBGC or any other Person under Title IV of ERISA.

“Utilization Fee Period” means any period of time after the date hereof during which the used portion of the Total Revolving Commitments exceeds 50% of the Total Revolving Commitments.

“Utilization Fee Rate” has the meaning set forth in Section 2.07(b).

“Voting Stock” means capital stock of any class or classes (however designated) having ordinary voting power for the election of directors of the Borrower, other than stock having such power only by reason of the happening of a contingency.

“Wells Fargo” means Wells Fargo Bank, National Association, in its individual capacity.

Section 1.02 Accounting Terms and Determinations. Unless otherwise specified herein, all accounting terms used herein shall be interpreted, all accounting determinations hereunder shall be made, and all financial statements required to be delivered hereunder shall be prepared in accordance with generally accepted accounting principles as in effect from time to time, applied on a basis consistent (except for changes concurred in by the Borrower’s independent public accountants) with the most recent audited consolidated financial statements of the Borrower and its Subsidiaries delivered to the Lenders; provided that, if the Borrower

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notifies the Administrative Agent that the Borrower wishes to amend any covenant in Article V to eliminate the effect of any change in generally accepted accounting principles on the operation of such covenant (or if the Administrative Agent notifies the Borrower that the Required Lenders wish to amend Article V for such purpose), then the Borrower’s compliance with such covenant shall be determined on the basis of generally accepted accounting principles in effect immediately before the relevant change in generally accepted accounting principles became effective, until either such notice is withdrawn or such covenant is amended in a manner satisfactory to the Borrower and the Required Lenders.

Section 1.03 Types of Borrowings. The term “Borrowing” denotes the aggregation of Loans of one or more Lenders to be made to the Borrower pursuant to Article II on a single date and, in the case of LIBOR Loans, for a single Interest Period. Borrowings may be classified for purposes of this Agreement by reference to the pricing of Loans comprising such Borrowing (e.g., a “Base Rate Borrowing” is a Borrowing comprised of Base Rate Loans, and a “LIBOR Borrowing” is a Borrowing comprised of LIBOR Loans).

ARTICLE II

THE CREDITS

Section 2.01 Commitments to Lend.

(a) Revolving Loans. During the Revolving Loan Availability Period, each Lender severally agrees, on the terms and conditions set forth in this Agreement, to make Revolving Loans to the Borrower pursuant to this Section 2.01(a) from time to time in amounts such that the aggregate principal amount of Revolving Loans by such Lender shall not exceed the amount of its Revolving Commitment less such Lender’s Revolving Commitment Percentage of all Letter of Credit Obligations outstanding at such time. Each Borrowing under this Section 2.01(a) shall be in an aggregate principal amount of $5,000,000 or any larger multiple of $1,000,000 (or in the remaining unused portion of the Revolving Commitments) and shall be made from the several Lenders ratably in proportion to their respective Revolving Commitments. Within the foregoing limits, the Borrower may borrow under this Section 2.01, repay, or to the extent permitted by Section 2.10, prepay Loans and reborrow at any time during the Revolving Loan Availability Period under this Section 2.01(a).

(b) Term Loans. During the Term Loan Availability Period, each Lender severally agrees, on the terms and conditions set forth in this Agreement, to make Term Loans to the Borrower pursuant to this Section 2.01(b) from time to time in amounts such that the aggregate principal amount of Term Loans by such Lender shall not exceed the amount of its Term Commitment. Each Borrowing under this Section 2.01(b) shall be made from the several Lenders ratably in proportion to their respective Term Loan Commitments. Borrower shall not be entitled to more than two (2) separate Borrowings from the Lenders under this Section 2.01(b). Amounts repaid on the Term Loans may not be reborrowed.

Section 2.02 Notice of Borrowings.

(a) Notice of Borrowings. The Borrower shall give the Administrative Agent

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notice (a “Notice of Borrowing”) not later than (x) 12:00 noon (Chicago time) on the date of each Base Rate Borrowing and (y) 1:00 P.M. (Chicago time) on the third Business Day before each LIBOR Borrowing, specifying:

(i) the date of such Borrowing, which shall be a Business Day

(ii) the aggregate amount of such Borrowing,

(iii) whether the Loans comprising such Borrowing are to be Revolving Loans or Term Loans,

(iv) whether the Loans comprising such Borrowing are to be Base Rate Loans or LIBOR Loans, and

(v) in the case of a LIBOR Borrowing, the duration of the Interest Period applicable thereto, subject to the provisions of the definition of Interest Period.

(b) Conversion and Continuation of Outstanding Advances. Base Rate Borrowings shall continue as Base Rate Borrowings unless and until such Base Rate Borrowings are converted into LIBOR Loans pursuant to this Section 2.02 or are repaid in accordance with this Article II. Each LIBOR Borrowing shall continue as a LIBOR Borrowing until the end of the then applicable Interest Period therefor, at which time such LIBOR Borrowing shall be automatically converted into a Base Rate Borrowing unless (x) such LIBOR Borrowing is or was repaid in accordance with this Article II or (y) the Borrower shall have given the Administrative Agent a Conversion/Continuation Notice (as defined below) requesting that, at the end of such Interest Period, such LIBOR Borrowing continue as a LIBOR Borrowing for the same or another Interest Period. The Borrower may elect from time to time to convert all or any part of a Base Rate Borrowing into a LIBOR Borrowing, provided that the resulting Borrowings shall be in a minimum amount of $5,000,000. The Borrower shall give the Administrative Agent irrevocable notice (a “Conversion/Continuation Notice”) of each conversion of a Base Rate Borrowing into a LIBOR Borrowing or continuation of a LIBOR Borrowing not later than 1:00 P.M. (Chicago time) at least three Business Days prior to the date of the requested conversion or continuation, specifying:

(i) the requested date, which shall be a Business Day, of such conversion or continuation,

(ii) the aggregate amount of the Borrowing which is to be converted or continued and whether such Borrowing is a Base Rate Borrowing or a LIBOR Borrowing, and

(iii) the amount of such Borrowing which is to be converted into or continued as a LIBOR Borrowing and the duration of the Interest Period applicable thereto.

In no event shall Borrower be permitted more than eight (8) Interest Periods outstanding at any one time under this Agreement.

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Section 2.03 Notice to Lenders; Funding of Loans.

(a) Upon receipt of a Notice of Borrowing the Administrative Agent shall promptly notify each Lender of the contents thereof and of such Lender’s share of such Borrowing and such Notice of Borrowing shall not thereafter be revocable by the Borrower.

(b) Not later than 2:00 P.M. (Chicago time) on the date of each Borrowing, each Lender therein shall (except as provided in subsection (c) of this Section) make available its share of such Borrowing, in Federal or other funds immediately available in San Francisco, California, to the Administrative Agent at its address specified in or pursuant to Section 9.01. Unless the Administrative Agent determines that any applicable condition specified in Article III has not been satisfied, the Administrative Agent will make the funds so received from the Lenders available to the Borrower at the Administrative Agent’s aforesaid address.

(c) If new Loans are to be made hereunder on a day on which the Borrower is to prepay or repay all or any part of outstanding Loans, the Lenders shall apply the proceeds of the new Loans to make such repayment and only an amount equal to the difference (if any) between the amount being borrowed and the amount being prepaid or repaid shall be made available by the Lenders to the Administrative Agent as provided in subsection (b), or remitted by the Borrower to the Administrative Agent as provided in Section 2.12, as the case may be. In such case, the incurrence of such new Loans and the prepayment or repayment of such outstanding Loans shall be deemed to have occurred simultaneously.

(d) Unless the Administrative Agent shall have received notice from a Lender prior to the date of any Borrowing that such Lender will not make available to the Administrative Agent such Lender’s share of such Borrowing, the Administrative Agent may assume that such Lender has made such share available to the Administrative Agent on the date of such Borrowing in accordance with subsections (b) and (c) of this Section 2.03 and the Administrative Agent may, in reliance upon such assumption, make available to the Borrower on such date a corresponding amount. If and to the extent that such Lender shall not have so made such share available to the Administrative Agent, such Lender and the Borrower severally agree to repay to the Administrative Agent forthwith on demand such corresponding amount together with interest thereon, for each day from the date such amount is made available to the Borrower until the date such amount is repaid to the Administrative Agent, at (i) in the case of the Borrower, a rate per annum equal to the interest rate applicable thereto pursuant to Section 2.06 and (ii) in the case of such Lender, the Federal Funds Effective Rate. If such Lender shall repay to the Administrative Agent such corresponding amount, such amount so repaid shall constitute such Lender’s Loan included in such Borrowing for purposes of this Agreement.

Section 2.04 Notes.

(a) The Revolving Loans of each Lender shall be evidenced by a single Revolving Note payable to the order of such Lender for the account of its Applicable Lending Office in an amount equal to the aggregate unpaid principal amount of such Lender’s Revolving Commitment. The Term Loans of each Lender shall be evidenced by a single Term Note payable to the order of such Lender for the account of its Applicable Lending Office in an amount equal to the aggregate unpaid principal amount of such Lender’s Term Commitment.

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