Document:

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                                                                   EXHIBIT 10.38

                                CREDIT AGREEMENT

        THIS AGREEMENT is entered into as of April 10, 2001, by and between
GEN-PROBE INCORPORATED, a Delaware corporation ("Gen-Probe"), and GEN-PROBE
SALES & SERVICE, INC., a Delaware corporation ("Gen-Probe Sales") (Gen-Probe and
Gen Probe Sales may be referred to collectively as "Borrowers" and individually
as "Borrower"), and WELLS FARGO BANK, NATIONAL ASSOCIATION ("Bank").

                                    RECITALS

        Borrowers have requested from Bank the credit accommodation described
below, and Bank has agreed to provide such credit accommodation to Borrowers on
the terms and conditions contained herein;

        NOW, THEREFORE, for valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, Bank and Borrowers hereby agree to the
following which shall be deemed to amend and restate the Prior Credit Agreement
dated July 1, 1999, as amended, between Bank and Gen-Probe (the "Prior Credit
Agreement"):

                                    ARTICLE I
                                  CREDIT TERMS

        SECTION 1.1. LINE OF CREDIT.

               (a) Line of Credit. Subject to the terms and conditions of this
Agreement, Bank hereby agrees to make advances to Borrowers from time to time up
to and including July 1, 2002, not to exceed at any time the aggregate principal
amount of Ten Million Dollars ($10,000,000.00) ("Line of Credit"), the proceeds
of which shall be used to finance Borrowers' working capital requirements.
Borrowers' obligation to repay advances under the Line of Credit shall be
evidenced by a promissory note substantially in the form of Exhibit A attached
hereto ("Line of Credit Note"), all terms of which are incorporated herein by
this reference. Outstanding advances under the "Line of Credit" under the Prior
Credit Agreement shall be deemed outstanding advances under the Line of Credit
under this Agreement. Bank hereby acknowledges and agrees that Borrowers may
terminate the Line of Credit at any time by giving two (2) days written notice
to Bank, at which time all amounts outstanding thereunder shall immediately
become due and payable in full.

               (b) Limitation on Borrowings. Outstanding borrowings under the
Line of Credit, to a maximum of the principal amount set forth above, shall not
at any time exceed a borrowing base (the "Borrowing Base") which is an aggregate
of eighty percent (80%) of Borrowers' Eligible Accounts Receivable (as defined
below). All of the foregoing shall be determined by Bank upon receipt and review
of all collateral reports required hereunder and such other documents and
collateral information as Bank may from time to time require. Borrower
acknowledges that the Borrowing Base was established by Bank with the
understanding that, among other items, the aggregate of all returns, rebates,
discounts, credits and allowances for the immediately preceding three (3) months
at all times shall be less than five percent (5%) of Borrowers' gross sales for
said period. If such dilution of Borrowers' accounts for the immediately
preceding three (3) months at any time exceeds five percent (5%) of Borrowers'
gross sales for said period, or if there at any time exists any other matters,
events, conditions or

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contingencies which Bank reasonably believes may affect payment of any portion
of any Borrower's accounts, Bank, in its sole discretion, may reduce the
foregoing advance rate to a percentage appropriate to reflect such additional
dilution and/or establish additional reserves against Borrowers' Eligible
Accounts Receivable.

        As used herein, "Borrowers' Eligible Accounts Receivable" shall consist
solely of trade accounts of a Borrower which (1) have been created in the
ordinary course of such Borrower's business or were created in the ordinary
course of Gen-Probe's business and purchased by Gen-Probe Sales, (2) upon which
the right of such Borrower to receive payment is absolute and not contingent
upon the fulfillment of any condition whatsoever, and in which Bank has a
perfected security interest of first priority, and shall not include:

               (i) any account which is past due more than twice such Borrower's
        standard selling terms, except with respect to any account for which
        such Borrower has provided extended payment terms not to exceed one
        hundred eighty (180) days, any such account which is more than thirty
        (30) days past due;

               (ii) that portion of any account for which there exists any right
        of setoff, defense or discount (except regular discounts allowed in the
        ordinary course of business to promote prompt payment) or for which any
        defense or counterclaim has been asserted;

               (iii) any account which represents an obligation of any state or
        municipal government or of the United States government or any political
        subdivision thereof, except for (1) accounts which represent obligations
        of the United States government and for which the assignment provisions
        of the Federal Assignment of Claims Act, as amended or recodified from
        time to time, have been complied with to Bank's satisfaction, and (2)
        such government accounts which would not be eligible for inclusion in
        the Borrowing Base under subdivision (1), but which Bank agrees not to
        exclude from the Borrowing Base under this paragraph (iii), which in the
        aggregate shall not exceed fifteen percent (15%) of the Borrowing Base;

               (iv) any account which represents an obligation of an account
        debtor located in a foreign country, except for (1) accounts which
        represent obligations of an account debtor located in the Canadian
        provinces of Alberta, British Columbia, Manitoba, Ontario, Saskatchewan
        or the Yukon Territory so long as, in Bank's determination, such
        Canadian jurisdictions recognize Bank's first priority security interest
        in and right to collect such account as a consequence of any security
        agreements and UCC filings in favor of Bank, (2) any such foreign
        account which, in Bank's determination, is supported by a letter of
        credit or insured under a policy of foreign credit insurance, in each
        case in form, substance and issued by a party acceptable to Bank, and
        (3) such foreign accounts which would not be eligible for inclusion in
        the Borrowing Base under subdivisions (1) or (2), but which Bank agrees
        not to exclude from the Borrowing Base under this paragraph (iv), which
        in the aggregate shall not exceed ten percent (10%) of the Borrowing
        Base;

               (v) any account which arises from the sale or lease to or
        performance of services for, or represents an obligation of, an
        employee, affiliate, partner, member, parent or subsidiary of any
        Borrower;

               (vi) that portion of any account, which represents interim or
        progress billings or retention rights on the part of the account debtor;

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               (vii) any account which represents an obligation of any account
        debtor when twenty percent (20%) or more of Borrowers' accounts from
        such account debtor are not eligible pursuant to (i) above;

               (viii) that portion of any account from an account debtor which
        represents the amount by which Borrowers' total accounts from said
        account debtor exceeds twenty-five percent (25%) of Borrowers' total
        accounts;

               (ix) any account deemed ineligible by Bank when Bank, in its sole
        discretion, deems the creditworthiness or financial condition of the
        account debtor, or the industry in which the account debtor is engaged,
        to be unsatisfactory.

        (c) Borrowing and Repayment. Borrower may from time to time during the
term of the Line of Credit borrow, partially or wholly repay its outstanding
borrowings, and reborrow, subject to all of the limitations, terms and
conditions contained herein or in the Line of Credit Note; provided however,
that the total outstanding borrowings under the Line of Credit shall not at any
time exceed the maximum principal amount available thereunder, as set forth
above.

        SECTION 1.2. INTEREST/FEES.

        (a) Interest. The outstanding principal balance of the Line of Credit
shall bear interest at the rate of interest set forth in the Line of Credit
Note.

        (b) Computation and Payment. Interest shall be computed on the basis of
a 360-day year, actual days elapsed. Interest shall be payable at the times and
place set forth in each promissory note or other instrument required hereby.

        (c) Commitment Fees. Borrowers shall pay to Bank a non-refundable
commitment fee for the Line of Credit equal to Twenty-five Thousand Dollars
($25,000.00), which fee shall be due and payable in full upon the execution of
this Agreement by Borrowers.

        (d) Unused Commitment Fee. Borrowers shall pay to Bank a fee initially
equal to .357% per annum (computed on the basis of a 360-day year, actual days
elapsed) on the average daily unused amount of the Line of Credit, which fee
shall be calculated on a calendar quarterly basis by Bank and shall be due and
payable by Borrowers in arrears on the tenth day of the next succeeding calendar
quarter.

        Bank shall adjust the percentage per annum used to determine the amount
of the fee on a quarterly basis, commencing with Borrowers' fiscal quarter
ending March 31, 2001, if required to reflect a change in Borrower's ratio of
Funded Debt to EBITDA (as defined in Section 4.9(e) below), in accordance with
the following grid:

        Funded Debt to EBITDA                      Percentage

        Less than .75 to 1.0                       .250

        Greater than or equal to
        .75 to 1.0, but less
        than 1.50 to 1.0                           .375

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        Greater than or equal to
        1.50 to 1.0, but less
        than 2.00 to 1.0                           .375

        Greater than or equal to
        2.00 to 1.0                                .500

        Each such adjustment shall be effective on the first Business Day (as
defined in the Line of Credit Note) following the date on which Bank receives
Borrowers' most current fiscal quarter-end financial statements in accordance
with Section 4.3 below.

        SECTION 1.3. COLLECTION OF PAYMENTS. Borrowers authorize Bank to collect
all interest and fees due under each credit subject hereto by charging
Gen-Probe's deposit account number 4721-117042 with Bank, or any other deposit
account maintained by Borrowers or either of them with Bank, for the full amount
thereof. Should there be insufficient funds in any such deposit account to pay
all such sums when due, the full amount of such deficiency shall be immediately
due and payable by Borrowers.

        SECTION 1.4. COLLATERAL.

        As security for all indebtedness of Borrowers to Bank under the Line of
Credit, each Borrower hereby grants to Bank security interests of first priority
in all of its accounts receivable and other rights to payment, general
intangibles, deposit accounts, inventory and equipment. All of the foregoing
shall be evidenced by and subject to the terms of such security agreements,
financing statements and other documents as Bank shall reasonably require, all
in form and substance satisfactory to Bank. Borrower shall reimburse Bank
immediately upon demand for all reasonable costs and expenses incurred by Bank
in connection with any of the foregoing security, including without limitation,
filing fees and costs of appraisals and audits.

                                   ARTICLE II
                         REPRESENTATIONS AND WARRANTIES

        Each Borrower makes the following representations and warranties to
Bank, which representations and warranties shall survive the execution of this
Agreement and shall continue in full force and effect until the full and final
payment, and satisfaction and discharge, of all obligations of Borrowers to Bank
subject to this Agreement.

        SECTION 2.1. LEGAL STATUS. Borrowers are each corporations, duly
organized and existing and in good standing under the laws of the State of
Delaware, and are each qualified or licensed to do business (and are each in
good standing as a foreign corporation, if applicable) in all jurisdictions in
which such qualification or licensing is required or in which the failure to so
qualify or to be so licensed could have a material adverse effect on any
Borrower.

        SECTION 2.2. AUTHORIZATION AND VALIDITY. This Agreement, the Line of
Credit Note and each other document, contract and instrument required hereby or
at any time hereafter delivered to Bank in connection herewith (collectively,
the "Loan Documents") have been duly authorized, and upon their execution and
delivery in accordance with the provisions hereof will constitute legal, valid
and binding agreements and obligations of Borrowers or the party which executes
the same, enforceable in accordance with their respective terms, except as such
enforceability may be limited by applicable bankruptcy, insolvency, moratorium
or

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similar laws affecting the rights of creditors generally and by equitable
principles regardless of whether considered in a proceeding in equity or at law.

        SECTION 2.3. NO VIOLATION. The execution, delivery and performance by
Borrowers of each of the Loan Documents do not violate any provision of any law
or regulation, or contravene any provision of the Articles of Incorporation or
By-Laws of any Borrower, or result in any breach of or default under any
contract, obligation, indenture or other instrument to which any Borrower is a
party or by which any Borrower may be bound.

        SECTION 2.4. LITIGATION. There are no pending, or to the best of
Borrowers' knowledge threatened, actions, claims, investigations, suits or
proceedings by or before any governmental authority, arbitrator, court or
administrative agency which could reasonably be expected to have a material
adverse effect on the financial condition or operation of any Borrower other
than those disclosed by Borrowers to Bank in writing prior to the date hereof.

        SECTION 2.5. CORRECTNESS OF FINANCIAL STATEMENT. The financial statement
of Borrowers dated December 31, 2000, a true copy of which has been delivered by
Borrowers to Bank prior to the date hereof, (a) is complete and correct and
presents fairly in all material respects the financial condition of Borrowers,
(b) discloses all liabilities of Borrowers that are required to be reflected or
reserved against under generally accepted accounting principles, whether
liquidated or unliquidated, fixed or contingent, and (c) has been prepared in
accordance with generally accepted accounting principles consistently applied.
Since the date of such financial statement there has been no material adverse
change in the financial condition of any Borrower, nor has any Borrower
mortgaged, pledged, granted a security interest in or otherwise encumbered any
of its assets or properties except in favor of Bank or as otherwise disclosed to
Bank in writing prior to the date hereof.

        SECTION 2.6. INCOME TAX RETURNS. No Borrower has knowledge of any
pending assessments or adjustments of any Borrower's income tax payable with
respect to any year.

        SECTION 2.7. NO SUBORDINATION. There is no agreement, indenture,
contract or instrument to which any Borrower is a party or by which any Borrower
may be bound that requires the subordination in right of payment of any
Borrower's obligations subject to this Agreement to any other obligation of any
Borrower.

        SECTION 2.8. PERMITS, FRANCHISES. Each Borrower possesses, and will
hereafter possess, all material permits, consents, approvals, franchises and
licenses required and rights to all trademarks, trade names, patents, and
fictitious names, if any, necessary to enable it to conduct the business in
which it is now engaged in compliance in all material respects with applicable
law.

      SECTION 2.9. ERISA. Each Borrower is in compliance in all material
respects with all applicable provisions of the Employee Retirement Income
Security Act of 1974, as amended or recodified from time to time ("ERISA"); no
Borrower has violated in any material respect any provision of any employee
Ipension benefit plan (as defined in ERISA Section 3(2)) maintained or
contributed to by any Borrower (each, a "Plan"); no Reportable Event as defined
in ERISA has occurred and is continuing with respect to any Plan initiated by
any Borrower; each Borrower has met its minimum funding requirements under ERISA
with respect to each Plan; and each Plan will be able to fulfill its benefit
obligations as they come due in accordance with the Plan documents and under
generally accepted accounting principles.

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        SECTION 2.10. OTHER OBLIGATIONS. No Borrower is in default on any
obligation for borrowed money, any purchase money obligation or any other
material lease, commitment, contract, instrument or obligation.

        SECTION 2.11. ENVIRONMENTAL MATTERS. Except as disclosed by Borrowers to
Bank in writing prior to the date hereof, Borrowers are each in compliance in
all material respects with all applicable federal or state environmental,
hazardous waste, health and safety statutes, and any rules or regulations
adopted pursuant thereto, which govern or affect any Borrower's operations
and/or properties, including without limitation, the Comprehensive Environmental
Response, Compensation and Liability Act of 1980, the Superfund Amendments and
Reauthorization Act of 1986, the Federal Resource Conservation and Recovery Act
of 1976, and the Federal Toxic Substances Control Act, as any of the same may be
amended, modified or supplemented from time to time. None of the operations of
any Borrower is the subject of any federal or state investigation evaluating
whether any remedial action involving a material expenditure is needed to
respond to a release of any toxic or hazardous waste or substance into the
environment. To the best of Borrowers' knowledge, no Borrower has any material
contingent liability in connection with any release of any toxic or hazardous
waste or substance into the environment.

                                   ARTICLE III
                                   CONDITIONS

        SECTION 3.1. CONDITIONS OF INITIAL EXTENSION OF CREDIT. The obligation
of Bank to extend any credit contemplated by this Agreement is subject to the
fulfillment to Bank's satisfaction of all of the following conditions:

               (a) Approval of Bank Counsel. All legal matters incidental to the
extension of credit by Bank shall be satisfactory to Bank's counsel.

               (b) Documentation. Bank shall have received, in form and
substance satisfactory to Bank, each of the following, duly executed:

               (i) This Agreement and the Line of Credit Note.

               (ii) Corporate Borrowing Resolutions.

               (iii) Certificates of Incumbency.

               (iv) Articles of Incorporation.

               (v) Security Agreements: Equipment.

               (vi) Continuing Security Agreements: Rights to Payment and
                    Inventory.

               (vii) UCC Financing Statements.

               (viii) Certificates of Status of Foreign Corporation.

               (ix) Such other documents as Bank may require under any other
                    Section of this Agreement.

               (c) Financial Condition. There shall have been no material
adverse change, as determined by Bank, in the financial condition or business of
any Borrower, nor any material decline, as determined by Bank, in the market
value of any collateral required hereunder or a substantial or material portion
of the assets of any Borrower.

               (d) Insurance. Borrowers shall have delivered to Bank evidence of
insurance coverage on all of each Borrower's property, in form, substance,
amounts, covering risks and issued by

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companies reasonably satisfactory to Bank, and where required by Bank, with loss
payable endorsements in favor of Bank.

        SECTION 3.2. CONDITIONS OF EACH EXTENSION OF CREDIT. The obligation of
Bank to make each extension of credit requested by Borrowers hereunder shall be
subject to the fulfillment to Bank's satisfaction of each of the following
conditions:

        (a) Compliance. The representations and warranties contained herein and
in each of the other Loan Documents shall be true on and as of the date of the
signing of this Agreement and on the date of each extension of credit by Bank
pursuant hereto, with the same effect as though such representations and
warranties had been made on and as of each such date, and on each such date, no
Event of Default as defined herein, and no condition, event or act which with
the giving of notice or the passage of time or both would constitute such an
Event of Default, shall have occurred and be continuing or shall exist.

        (b) Documentation. Bank shall have received all additional documents
which may reasonably be required in connection with such extension of credit.
The selection by Borrowers of an interest rate option under the Line of Credit
Note in and of itself shall not be deemed a new extension of credit hereunder.

                                   ARTICLE IV
                              AFFIRMATIVE COVENANTS

        Each Borrower covenants that so long as Bank remains committed to extend
credit to Borrowers pursuant hereto, or any liabilities (whether direct or
contingent, liquidated or unliquidated) of Borrowers to Bank under any of the
Loan Documents remain outstanding, and until payment in full of all obligations
of Borrowers subject hereto, unless Bank otherwise consents in writing:

        SECTION 4.1. PUNCTUAL PAYMENTS. Each Borrower shall punctually pay all
principal, interest, fees or other liabilities due under any of the Loan
Documents at the times and place and in the manner specified therein, and
immediately upon demand by Bank, the amount by which the outstanding principal
balance of any credit subject hereto at any time exceeds any limitation on
borrowings applicable thereto.

        SECTION 4.2. ACCOUNTING RECORDS. Each Borrower shall maintain adequate
books and records in accordance with generally accepted accounting principles
consistently applied, and permit any representative of Bank, at any reasonable
time upon prior notice, to inspect, audit and examine such books and records, to
make copies of the same, and to inspect the properties of each Borrower.

        SECTION 4.3. FINANCIAL STATEMENTS. Each Borrower shall provide to Bank
all of the following, in form and detail satisfactory to Bank:

        (a) not later than 90 days after and as of the end of each fiscal year,
an unqualified audited consolidated financial statement of Borrowers, prepared
by a nationally recognized "Big 5" certified public accountant firm or other
accountants acceptable to Bank, to include a balance sheet, income statement and
statement of cash flows;

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        (b) not later than 45 days after and as of the end of each fiscal
quarter, an unaudited consolidated financial statement of Borrowers, prepared by
Borrowers, to include balance sheet and income statement;

        (c) not later than 30 days after and as of the end of each month, on a
consolidated basis, a Borrowing Base certificate, an aged listing of accounts
receivable and accounts payable, and a reconciliation of accounts

        (d) not later than 30 days after and as of each June 30 and December 31,
a list of the names and addresses of all of each Borrower's account debtors;

        (e) contemporaneously with each annual and fiscal quarter end financial
statement of Borrowers required hereby, a certificate of the president or chief
financial officer of Borrowers that said financial statements are accurate in
all material respects and that to the best knowledge of such officer after
diligent inquiry there exists no Event of Default nor any condition, act or
event which with the giving of notice or the passage of time or both would
constitute an Event of Default, together with a calculation of each financial
covenant set forth in Section 4.9 below; provided however, if an Event of
Default or a condition, act or event which with the giving of notice or the
passage of time or both would constitute an Event of Default does exist, such
officer shall describe such condition, act or event in the certificate; and
provided further, that such disclosure and description of such condition, act or
event shall not obligate Bank to waive its rights and remedies hereunder in
connection therewith; and

        (f) from time to time such other information as Bank may reasonably
request.

        SECTION 4.4. COMPLIANCE. Each Borrower shall preserve and maintain all
licenses, permits, governmental approvals, rights, privileges and franchises
necessary for the conduct of its business; and comply with the provisions of all
documents pursuant to which it is organized and/or which govern its continued
existence and with the requirements of all laws, rules, regulations and orders
of any governmental authority applicable to it and/or its business
non-compliance with which could have a material adverse effect on any Borrower.

        SECTION 4.5. INSURANCE. Each Borrower shall maintain and keep in force
insurance of the types and in amounts customarily carried in lines of business
similar to that of Borrowers, including but not limited to fire, extended
coverage, public liability, flood, property damage and workers' compensation,
with all such insurance carried with companies and in amounts reasonably
satisfactory to Bank, and deliver to Bank from time to time at Bank's request
schedules setting forth all insurance then in effect.

        SECTION 4.6. FACILITIES. Each Borrower shall keep all properties useful
or necessary to its business in good repair and condition, and from time to time
make necessary repairs, renewals and replacements thereto so that such
properties shall be fully and efficiently preserved and maintained.

        SECTION 4.7. TAXES AND OTHER LIABILITIES. Each Borrower shall pay and
discharge when due any and all indebtedness, obligations, assessments and taxes,
both real or personal, including without limitation federal and state income
taxes and state and local property taxes and assessments, except such (a) as a
Borrower may in good faith contest or as to which a bona fide dispute may arise,
and (b) for which Borrowers have made provision, to Bank's satisfaction, for
eventual payment thereof in the event any Borrower is obligated to make such
payment.

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        SECTION 4.8. LITIGATION. Each Borrower shall promptly give notice in
writing to Bank of any litigation pending or threatened against any Borrower
with a claim in excess of $500,000.00.

        SECTION 4.9. FINANCIAL CONDITION. Each Borrower shall maintain
Borrowers' consolidated financial condition as follows using generally accepted
accounting principles consistently applied and used consistently with prior
practices (except to the extent modified by the definitions herein), with
compliance determined commencing with Borrowers' financial statements for the
period ending as of March 31, 2001:

        (a) Tangible Net Worth as of March 31, 2001, June 30, 2001 and September
30, 2001 not less than the sum of $55,000,000.00 plus one hundred percent (100%)
of the proceeds of any equity offering by any Borrower on a cumulative basis
after December 31, 2000, and as of December 31, 2001 and each fiscal quarter end
thereafter not less than the sum of $65,000,000.00 plus fifty percent (50%) of
Borrower's quarterly net income on a cumulative basis after September 30, 2001
(without making any deduction for, or otherwise giving effect to, any quarterly
net loss), plus one hundred percent (100%) of the proceeds of any equity
offering by any Borrower on a cumulative basis after December 31, 2000, with
"Tangible Net Worth" defined as the aggregate of total stockholders' equity plus
subordinated debt less any intangible assets (intangible assets shall include,
without limitation, goodwill, patents, purchased intangibles and capitalized
software development costs), less any treasury stock and less any obligations
owing from stockholders, employees and/or affiliates.

        (b) Total Liabilities divided by Tangible Net Worth not at any time
greater than .80 to 1.0, with "Total Liabilities" defined as the aggregate of
current liabilities and non-current liabilities less subordinated debt, and with
"Tangible Net Worth" as defined above.

        (c) Current Ratio not at any time less than 1.50 to 1.0, with "Current
Ratio" defined as total current assets divided by total current liabilities
(current liabilities shall include, without limitation, all amounts outstanding
under the Line of Credit).

        (d) EBITDA not less than $9,000,000.00 as of March 31, 2001, not less
than $11,000,000.00 as of June 30, 2001, not less than $13,000,000.00 as of
September 30, 2001, and not less than $15,000,000.00 as of each fiscal quarter
end thereafter, calculated on a rolling four-quarter basis, with "EBITDA"
defined as net profit before tax plus interest expense (net of capitalized
interest expense), depreciation expense and amortization expense.

        (e) Funded Debt/EBITDA Coverage Ratio not greater than 2.5 to 1.0 as of
March 31, 2001, June 30, 2001 and September 30, 2001, and not greater than 1.50
to 1.0 as of December 31, 2001 and each fiscal quarter end thereafter, with
"Funded Debt" defined as all indebtedness for borrowed money, including without
limitation all amounts outstanding under the Line of Credit (calculated as the
average daily balance outstanding under the Line of Credit during the last month
of each fiscal quarter) plus capital leases; with "EBITDA" as defined above, and
with "Funded Debt/EBITDA Coverage Ratio" defined as Funded Debt divided by
EBITDA.

        (f) Maximum cumulative year-to-date pre-tax loss as of June 30, 2001 not
greater than $5,000,000.00.

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        (g) Net loss after taxes as of the fiscal quarter ending September 30,
2001 not to exceed $1,500,000.00.

        (h) Net income after taxes not less than $1.00 on a quarterly basis
determined as of each fiscal quarter end commencing with the fiscal quarter
ending December 31, 2001.

        SECTION 4.10. NOTICE TO BANK. Each Borrower shall promptly (but in no
event more than five (5) business days after any Borrower has knowledge of each
such event or matter) give written notice to Bank in reasonable detail of: (a)
the occurrence of any Event of Default, or any condition, event or act which
with the giving of notice or the passage of time or both would constitute an
Event of Default; (b) any change in the name or the organizational structure of
any Borrower; (c) the occurrence and nature of any Reportable Event or
Prohibited Transaction, each as defined in ERISA, or any funding deficiency with
respect to any Plan, in each case involving amounts greater than $10,000.00 in
the aggregate for all such events combined; or (d) any termination or
cancellation of any insurance policy which any Borrower is required to maintain,
or any uninsured or partially uninsured loss through liability or property
damage, or through fire, theft or any other cause affecting any Borrower's
property in excess of an aggregate of $1,000,000.00.

                                    ARTICLE V
                               NEGATIVE COVENANTS

        Each Borrower further covenants that so long as Bank remains committed
to extend credit to Borrowers pursuant hereto, or any liabilities (whether
direct or contingent, liquidated or unliquidated) of Borrowers to Bank under any
of the Loan Documents remain outstanding, and until payment in full of all
obligations of Borrowers subject hereto, without Bank's prior written consent:

        SECTION 5.1. USE OF FUNDS. Each Borrower will not use any of the
proceeds of any credit extended hereunder except for the purposes stated in
Article I hereof.

        SECTION 5.2. OTHER INDEBTEDNESS. Each Borrower will not create, incur,
assume or permit to exist any indebtedness or liabilities resulting from
borrowings, loans or advances, whether secured or unsecured, matured or
unmatured, liquidated or unliquidated, joint or several, except (a) the
liabilities of any Borrower to Bank, (b) any other liabilities of any Borrower
existing as of, and disclosed to Bank prior to, the date hereof, (c) trade
payables incurred in the ordinary course of any Borrower's business, (d)
indebtedness incurred from time to time from Gen-Probe's parent company, not to
exceed an aggregate of $4,000,000.00 at any time outstanding unless the portion
of such indebtedness in excess of $4,000,000.00 has been subordinated to all
indebtedness of Borrowers to Bank pursuant to the terms and conditions of a
subordination agreement in form and substance satisfactory to bank, and (e)
purchase money indebtedness up to $1,000,000.00 in the aggregate.

        SECTION 5.3. MERGER, CONSOLIDATION, TRANSFER OF ASSETS. Each Borrower
will not merge into or consolidate with any other entity; make any substantial
change in the nature of its business as conducted as of the date hereof; acquire
all or substantially all of the assets of any other entity; nor sell, lease,
transfer or otherwise dispose of all or a substantial or material portion of its
assets except in the ordinary course of its business.

                                      -10-
<PAGE>
        SECTION 5.4. GUARANTIES. Each Borrower will not guarantee or become
liable in any way as surety, endorser (other than as endorser of negotiable
instruments for deposit or collection in the ordinary course of business),
accommodation endorser or otherwise for, nor pledge or hypothecate any of its
assets as security for, any liabilities or obligations of any other person or
entity, except any of the foregoing in favor of Bank.

        SECTION 5.5. LOANS, ADVANCES, INVESTMENTS. Each Borrower will not make
any loans or advances to or investments in any person or entity, except (a) any
of the foregoing existing as of, and disclosed to Bank prior to, the date
hereof, (b) new investments in cash, cash equivalents and bonds of the same type
as those existing as of and disclosed to Bank prior to the date hereof, and (c)
any of the foregoing made to or in Gen-Probe Sales by Gen-Probe.

        SECTION 5.6. PLEDGE OF ASSETS. Each Borrower will not mortgage, pledge,
grant or permit to exist a security interest in, or lien upon, all or any
portion of its assets now owned or hereafter acquired, except (a) any of the
foregoing in favor of Bank, (b) any of the foregoing which is existing as of,
and disclosed to Bank in writing prior to, the date hereof, (c) purchase money
security interests to secure purchase money indebtedness up to $1,000,000.00 in
the aggregate, and (d) liens for property taxes, mechanics' liens, materialmen's
liens, warehousman's liens, repairman's liens and other similar liens, all of
which are not yet due and payable.

                                   ARTICLE VI
                                EVENTS OF DEFAULT

        SECTION 6.1. The occurrence of any of the following shall constitute an
"Event of Default" under this Agreement:

        (a) Any Borrower shall fail to pay when due any principal, interest,
fees or other amounts payable under any of the Loan Documents.

        (b) Any financial statement or certificate furnished to Bank in
connection with, or any representation or warranty made by any Borrower or any
other party under this Agreement or any other Loan Document shall prove to be
incorrect, false or misleading in any material respect when furnished or made.

        (c) Any default in the performance of or compliance with any obligation,
agreement or other provision contained herein or in any other Loan Document
(other than those referred to in subsections (a) and (b) above), and with
respect to any such default which by its nature can be cured, such default shall
continue for a period of twenty (20) days from its occurrence.

        (d) Any default in the payment or performance of any obligation, or any
defined event of default, under the terms of any contract or instrument (other
than any of the Loan Documents) pursuant to which any Borrower has incurred any
debt or other liability to Bank; or any default in the payment or performance of
any obligation, or any defined event of default, under the terms of any contract
or instrument pursuant to which any Borrower has incurred any debt or liability
to any person or entity other than Bank in excess of $1,000,000.00 for all such
defaults combined.

        (e) The filing of a notice of judgment lien against any Borrower; or the
recording of any abstract of judgment against any Borrower in any county in
which such Borrower has an interest

                                      -11-
<PAGE>
in real property; or the service of a notice of levy and/or of a writ of
attachment or execution, or other like process, against the assets of any
Borrower; or the entry of a judgment against any Borrower; provided, however,
that in each case within thirty (30) days of the creation of such judgment,
lien, levy, writ, execution or other process, or at least ten (10) days prior to
the date on which any assets could be lawfully sold in satisfaction thereof, the
debt or claim related thereto has not been satisfied or stayed pending appeal
and insured against in a manner satisfactory to Bank.

        (f) Any Borrower shall become insolvent, or shall suffer or consent to
or apply for the appointment of a receiver, trustee, custodian or liquidator of
itself or any of its property, or shall generally fail to pay its debts as they
become due, or shall make a general assignment for the benefit of creditors; any
Borrower shall file a voluntary petition in bankruptcy, or seeking
reorganization, in order to effect a plan or other arrangement with creditors or
any other relief under the Bankruptcy Reform Act, Title 11 of the United States
Code, as amended or recodified from time to time ("Bankruptcy Code"), or under
any state or federal law granting relief to debtors, whether now or hereafter in
effect; or any involuntary petition or proceeding pursuant to the Bankruptcy
Code or any other applicable state or federal law relating to bankruptcy,
reorganization or other relief for debtors is filed or commenced against any
Borrower, and such involuntary petition or proceeding is unopposed or is not
dismissed within sixty (60) days of its commencement (it being understood and
agreed, however, that Bank shall have no obligation to permit borrowings under
the Line of Credit during such sixty (60) day period), or any Borrower shall
file an answer admitting the jurisdiction of the court and the material
allegations of any involuntary petition; or any Borrower shall be adjudicated a
bankrupt, or an order for relief shall be entered against any Borrower by any
court of competent jurisdiction under the Bankruptcy Code or any other
applicable state or federal law relating to bankruptcy, reorganization or other
relief for debtors.

        (g) There shall exist or occur any event or condition which Bank in good
faith believes impairs, or is substantially likely to impair, the prospect of
payment or performance by Borrowers of its obligations under any of the Loan
Documents.

        (h) The dissolution or liquidation of any Borrower; or any Borrower, or
any of its directors, stockholders or members, shall take action seeking to
effect the dissolution or liquidation of any Borrower.

        (i) Any change in ownership during the term of this Agreement of an
aggregate of twenty-five percent (25%) or more of the common stock of Gen-Probe.

        (j) Gen-Probe shall at any time cease to own one hundred percent (100%)
of the stock of Gen-Probe Sales.

        SECTION 6.2. REMEDIES. Upon the occurrence of any Event of Default: (a)
all indebtedness of Borrowers under each of the Loan Documents, any term thereof
to the contrary notwithstanding, shall at Bank's option and without notice
become immediately due and payable without presentment, demand, protest or
notice of dishonor, all of which are hereby expressly waived by each Borrower;
(b) the obligation, if any, of Bank to extend any further credit under any of
the Loan Documents shall immediately cease and terminate; and (c) Bank shall
have all rights, powers and remedies available under each of the Loan Documents,
or accorded by law, including without limitation the right to resort to any or
all security for any credit subject hereto and to exercise any or all of the
rights of a beneficiary or secured party pursuant to applicable law. All rights,
powers and remedies of Bank may be exercised at any time by Bank and from

                                      -12-
<PAGE>
time to time after the occurrence of an Event of Default, are cumulative and not
exclusive, and shall be in addition to any other rights, powers or remedies
provided by law or equity.

                                   ARTICLE VII
                                  MISCELLANEOUS

        SECTION 7.1. NO WAIVER. No delay, failure or discontinuance of Bank in
exercising any right, power or remedy under any of the Loan Documents shall
affect or operate as a waiver of such right, power or remedy; nor shall any
single or partial exercise of any such right, power or remedy preclude, waive or
otherwise affect any other or further exercise thereof or the exercise of any
other right, power or remedy. Any waiver, permit, consent or approval of any
kind by Bank of any breach of or default under any of the Loan Documents must be
in writing and shall be effective only to the extent set forth in such writing.

        SECTION 7.2. NOTICES. All notices, requests and demands which any party
is required or may desire to give to any other party under any provision of this
Agreement must be in writing delivered to each party at the following address:

    BORROWERS:      GEN-PROBE INCORPORATED
                    10210 Genetic Center Drive
                    San Diego, CA 92121

                    GEN-PROBE  SALES & SERVICE, INC.
                    10210 Genetic Center Drive
                    San Diego, CA 92121

    BANK:           WELLS FARGO BANK, NATIONAL ASSOCIATION
                    San Diego Regional Commercial Banking Office
                    401 B Street, Suite 2201
                    San Diego, CA 92101

or to such other address as any party may designate by written notice to all
other parties. Each such notice, request and demand shall be deemed given or
made as follows: (a) if sent by hand delivery, upon delivery; (b) if sent by
mail, upon the earlier of the date of receipt or three (3) days after deposit in
the U.S. mail, first class and postage prepaid; and (c) if sent by telecopy,
upon receipt.

        SECTION 7.3. COSTS, EXPENSES AND ATTORNEYS' FEES. Borrowers shall pay to
Bank immediately upon demand the full amount of all payments, advances, charges,
costs and expenses, including reasonable attorneys' fees (to include outside
counsel fees and all allocated costs of Bank's in-house counsel), expended or
incurred by Bank in connection with (a) the negotiation and preparation of this
Agreement and the other Loan Documents to a maximum of $5,000.00, and the
preparation of any amendments and waivers hereto and thereto, (b) the
enforcement of Bank's rights and/or the collection of any amounts which become
due to Bank under any of the Loan Documents, and (c) the prosecution or defense
of any action in any way related to any of the Loan Documents, including without
limitation, any action for declaratory relief, whether incurred at the trial or
appellate level, in an arbitration proceeding or otherwise, and including any of
the foregoing incurred in connection with any bankruptcy proceeding (including
without limitation, any adversary proceeding, contested matter or motion brought
by Bank or any other person) relating to any Borrower or any other person or
entity.

                                      -13-
<PAGE>
        SECTION 7.4. SUCCESSORS, ASSIGNMENT. This Agreement shall be binding
upon and inure to the benefit of the heirs, executors, administrators, legal
representatives, successors and assigns of the parties; provided however, that
Borrowers may not assign or transfer their interests hereunder without Bank's
prior written consent. Bank reserves the right to sell, assign, transfer,
negotiate or grant participations in all or any part of, or any interest in,
Bank's rights and benefits under each of the Loan Documents. In connection
therewith, Bank may disclose all documents and information which Bank now has or
may hereafter acquire relating to the Line of Credit, any Borrower or its
business, or any collateral required hereunder. Bank shall use its best efforts
to cause any potential participant to execute a confidentiality agreement in
form and substance reasonably satisfactory to Borrowers.

        SECTION 7.5. ENTIRE AGREEMENT; AMENDMENT. This Agreement and the other
Loan Documents constitute the entire agreement between Borrowers and Bank with
respect to each credit subject hereto and supersede all prior negotiations,
communications, discussions and correspondence concerning the subject matter
hereof. This Agreement may be amended or modified only in writing signed by each
party hereto.

        SECTION 7.6. NO THIRD PARTY BENEFICIARIES. This Agreement is made and
entered into for the sole protection and benefit of the parties hereto and their
respective permitted successors and assigns, and no other person or entity shall
be a third party beneficiary of, or have any direct or indirect cause of action
or claim in connection with, this Agreement or any other of the Loan Documents
to which it is not a party.

        SECTION 7.7. TIME. Time is of the essence of each and every provision of
this Agreement and each other of the Loan Documents.

        SECTION 7.8. SEVERABILITY OF PROVISIONS. If any provision of this
Agreement shall be prohibited by or invalid under applicable law, such provision
shall be ineffective only to the extent of such prohibition or invalidity
without invalidating the remainder of such provision or any remaining provisions
of this Agreement.

        SECTION 7.9. COUNTERPARTS. This Agreement may be executed in any number
of counterparts, each of which when executed and delivered shall be deemed to be
an original, and all of which when taken together shall constitute one and the
same Agreement.

        SECTION 7.10. GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the laws of the State of California.

        SECTION 7.11. JOINT AND SEVERAL LIABILITY.

        (a) Each Borrower has determined and represents to Bank that it is in
its best interests and in pursuance of its legitimate business purposes to
induce Bank to extend credit pursuant to this Agreement. Each Borrower
acknowledges and represents that its business is related to the business of the
other Borrower, the availability of the commitments provided for herein benefits
all Borrowers, and advances and other credit extensions made hereunder will be
for and inure to the benefit of Borrowers, individually and as a group.

        (b) Each Borrower has determined and represents to Bank that it has, and
after giving effect to the transactions contemplated by this Agreement will
have, assets having a fair saleable value in excess of its debts, after giving
effect to any rights of contribution or

                                      -14-
<PAGE>
subrogation which may be available to such Borrower, and each Borrower has, and
will have, access to adequate capital for the conduct of its business and the
ability to pay its debts as such debts mature.

        (c) Each Borrower agrees that it is jointly and severally liable to Bank
for, and each Borrower agrees to pay to Bank when due the full amount of, all
indebtedness now existing or hereafter arising to Bank under or in connection
with the Line of Credit and all modifications, extensions and renewals thereof,
including without limitation all advances disbursed to any Borrower under the
Line of Credit, all interest which accrues thereon, and all fees, costs and
expenses chargeable to Borrowers or any of them in connection therewith.

        (d) The liability of each Borrower for the Line of Credit shall be
reinstated and revived and the rights of Bank shall continue if and to the
extent that for any reason any amount at any time paid on account of the Line of
Credit is rescinded or must otherwise be restored by Bank, whether as a result
of any proceedings in bankruptcy or reorganization or otherwise, all as though
such amount had not been paid.

        (e) Each Borrower authorizes Bank, without notice to or demand on such
Borrower, and without affecting such Borrower's liability for the Line of
Credit, from time to time to: (i) alter, compromise, extend, accelerate or
otherwise change the time for payment of, or otherwise change the terms of, the
liabilities and obligations of any other Borrower to Bank on account of the Line
of Credit; (ii) take and hold security from any other Borrower for the payment
of the Line of Credit, and exchange, enforce, waive, subordinate or release any
such security; (iii) apply such security and direct the order or manner of sale
thereof, including without limitation, a non-judicial sale permitted by the
terms of the controlling security agreement or deed of trust, as Bank in its
discretion may determine; (iv) release or substitute any one or more of the
endorsers or any guarantors of the Line of Credit, or any other party obligated
thereon; and (v) apply payments received by Bank from any other Borrower to
indebtedness of such other Borrower to Bank other than the Line of Credit.

        (f) Each Borrower represents and warrants to Bank that it has
established adequate means of obtaining from each other Borrower on a continuing
basis financial and other information pertaining to each other Borrower's
financial condition, and each Borrower agrees to keep adequately informed from
such means of any facts, events or circumstances which might in any way affect
its risks hereunder. Each Borrower further agrees that Bank shall have no
obligation to disclose to it any information or material about any other
Borrower which is acquired by Bank in any manner.

        (g) Each Borrower waives any right to require Bank to: (i) proceed
against any other Borrower or any other person; (ii) marshal assets or proceed
against or exhaust any security held from any other Borrower or any other
person; (iii) pursue any other remedy in Bank's power; (iv) apply payments
received by Bank from any other Borrower to the Line of Credit; or (v) make any
presentments or demands for performance, or give any notices of nonperformance,
protests, notices of protest or notices of dishonor in connection with the Line
of Credit.

        (h) Each Borrower waives any defense to its liability for the Line of
Credit based upon or arising by reason of: (i) any disability or other defense
of any other Borrower or any other person; (ii) the cessation or limitation from
any cause whatsoever, other than payment in full, of the liability of any other
Borrower for the Line of Credit; (iii) any lack of authority of any officer,
director, partner, agent or other person acting or purporting to act on behalf
of any other Borrower or any defect in the formation of any other Borrower; (iv)
the application by any other Borrower of the proceeds of the Line of Credit for
purposes other than the purposes intended or

                                      -15-
<PAGE>
understood by Bank or any Borrower; (v) any act or omission by Bank which
directly or indirectly results in or aids the discharge of any other Borrower by
operation of law or otherwise, or which in any way impairs or suspends any
rights or remedies of Bank against any other Borrower; (vi) any impairment of
the value of any interest in any security for the Line of Credit, including
without limitation, the failure to obtain or maintain perfection or recordation
of any interest in any such security, the release of any such security without
substitution, and/or the failure to preserve the value of, or to comply with
applicable law in disposing of, any such security; or (vii) any modification of
the obligations or liabilities of any other Borrower for the Line of Credit,
including without limitation the renewal, extension, acceleration or other
change in time for payment of, or other change in the terms of, the indebtedness
of any other Borrower for the Line of Credit, including increase or decrease of
the rate of interest thereon. Until the Line of Credit and all indebtedness of
each Borrower to Bank arising under or in connection with this Agreement shall
have been paid in full, no Borrower shall have any right of subrogation. Each
Borrower waives all rights and defenses it may have arising out of (A) any
election of remedies by Bank, even though that election of remedies, such as a
non-judicial foreclosure with respect to any security for the Line Credit,
destroys its rights of subrogation or its rights to proceed against any other
Borrower for reimbursement, or (B) any loss of rights it may suffer by reason of
any rights, powers or remedies of any other Borrower in connection with any
anti-deficiency laws or any other laws limiting, qualifying or discharging any
Borrower's indebtedness for the Line of Credit, whether by operation of law or
otherwise. Until the Line of Credit and all indebtedness of each Borrower to
Bank arising under or in connection with this Agreement shall have been paid in
full, each Borrower waives any right to enforce any remedy which Bank now has or
may hereafter have against any other Borrower or any other person, and waives
any benefit of, or any right to participate in, any security now or hereafter
held by Bank.

        (i) If any of the waivers herein is determined to be contrary to any
applicable law or public policy, such waiver shall be effective only to the
extent permitted by law.

        (j) It is the position of the Borrowers that each Borrower benefits from
the Line of Credit that has been made available by Bank under this Agreement and
from each extension of credit thereunder, regardless of whether such credit is
disbursed to a joint account of Borrowers or to or for the account of any
Borrower.

        SECTION 7.12. ARBITRATION.

        (a) Arbitration. The parties hereto agree, upon demand by any party, to
submit to binding arbitration all claims, disputes and controversies between or
among them (and their respective employees, officers, directors, attorneys, and
other agents), whether in tort, contract or otherwise arising out of or relating
to in any way (i) the loan and related Loan Documents which are the subject of
this Agreement and its negotiation, execution, collateralization,
administration, repayment, modification, extension, substitution, formation,
inducement, enforcement, default or termination; or (ii) requests for additional
credit.

        (b) Governing Rules. Any arbitration proceeding will (i) proceed in a
location in California selected by the American Arbitration Association ("AAA");
(ii) be governed by the Federal Arbitration Act (Title 9 of the United States
Code), notwithstanding any conflicting choice of law provision in any of the
documents between the parties; and (iii) be conducted by the AAA, or such other
administrator as the parties shall mutually agree upon, in accordance with the
AAA's commercial dispute resolution procedures, unless the claim or counterclaim
is at least $1,000,000.00 exclusive of claimed interest, arbitration fees and
costs in which case the arbitration shall be conducted in accordance with the
AAA's optional procedures for large, complex commercial disputes (the commercial
dispute resolution procedures or the optional

                                      -16-
<PAGE>
procedures for large, complex commercial disputes to be referred to, as
applicable, as the "Rules"). If there is any inconsistency between the terms
hereof and the Rules, the terms and procedures set forth herein shall control.
Any party who fails or refuses to submit to arbitration following a demand by
any other party shall bear all costs and expenses incurred by such other party
in compelling arbitration of any dispute. Nothing contained herein shall be
deemed to be a waiver by any party that is a bank of the protections afforded to
it under 12 U.S.C. Section 91 or any similar applicable state law.

        (c) No Waiver of Provisional Remedies, Self-Help and Foreclosure. The
arbitration requirement does not limit the right of any party to (i) foreclose
against real or personal property collateral; (ii) exercise self-help remedies
relating to collateral or proceeds of collateral such as setoff or repossession;
or (iii) obtain provisional or ancillary remedies such as replevin, injunctive
relief, attachment or the appointment of a receiver, before during or after the
pendency of any arbitration proceeding. This exclusion does not constitute a
waiver of the right or obligation of any party to submit any dispute to
arbitration or reference hereunder, including those arising from the exercise of
the actions detailed in sections (i), (ii) and (iii) of this paragraph.

        (d) Arbitrator Qualifications and Powers. Any arbitration proceeding in
which the amount in controversy is $5,000,000.00 or less will be decided by a
single arbitrator selected according to the Rules, and who shall not render an
award of greater than $5,000,000.00. Any dispute in which the amount in
controversy exceeds $5,000,000.00 shall be decided by majority vote of a panel
of three arbitrators; provided however, that all three arbitrators must actively
participate in all hearings and deliberations. The arbitrator will be a neutral
attorney licensed in the State of California or a neutral retired judge of the
state or federal judiciary of California, in either case with a minimum of ten
years experience in the substantive law applicable to the subject matter of the
dispute to be arbitrated. The arbitrator will determine whether or not an issue
is arbitratable and will give effect to the statutes of limitation in
determining any claim. In any arbitration proceeding the arbitrator will decide
(by documents only or with a hearing at the arbitrator's discretion) any
pre-hearing motions which are similar to motions to dismiss for failure to state
a claim or motions for summary adjudication. The arbitrator shall resolve all
disputes in accordance with the substantive law of California and may grant any
remedy or relief that a court of such state could order or grant within the
scope hereof and such ancillary relief as is necessary to make effective any
award. The arbitrator shall also have the power to award recovery of all costs
and fees, to impose sanctions and to take such other action as the arbitrator
deems necessary to the same extent a judge could pursuant to the Federal Rules
of Civil Procedure, the California Rules of Civil Procedure or other applicable
law. Judgment upon the award rendered by the arbitrator may be entered in any
court having jurisdiction. The institution and maintenance of an action for
judicial relief or pursuit of a provisional or ancillary remedy shall not
constitute a waiver of the right of any party, including the plaintiff, to
submit the controversy or claim to arbitration if any other party contests such
action for judicial relief.

        (e) Discovery. In any arbitration proceeding discovery will be permitted
in accordance with the Rules. All discovery shall be expressly limited to
matters directly relevant to the dispute being arbitrated and must be completed
no later than 20 days before the hearing date and within 180 days of the filing
of the dispute with the AAA. Any requests for an extension of the discovery
periods, or any discovery disputes, will be subject to final determination by
the arbitrator upon a showing that the request for discovery is essential for
the party's presentation and that no alternative means for obtaining information
is available.

                                      -17-
<PAGE>
        (f) Class Proceedings and Consolidations. The resolution of any dispute
arising pursuant to the terms of this Agreement shall be determined by a
separate arbitration proceeding and such dispute shall not be consolidated with
other disputes or included in any class proceeding.

        (g) Payment Of Arbitration Costs And Fees. The arbitrator shall award
all costs and expenses of the arbitration proceeding.

        (h) Real Property Collateral; Judicial Reference. Notwithstanding
anything herein to the contrary, no dispute shall be submitted to arbitration if
the dispute concerns indebtedness secured directly or indirectly, in whole or in
part, by any real property unless (i) the holder of the mortgage, lien or
security interest specifically elects in writing to proceed with the
arbitration, or (ii) all parties to the arbitration waive any rights or benefits
that might accrue to them by virtue of the single action rule statute of
California, thereby agreeing that all indebtedness and obligations of the
parties, and all mortgages, liens and security interests securing such
indebtedness and obligations, shall remain fully valid and enforceable. If any
such dispute is not submitted to arbitration, the dispute shall be referred to a
referee in accordance with California Code of Civil Procedure Section 638 et
seq., and this general reference agreement is intended to be specifically
enforceable in accordance with said Section 638. A referee with the
qualifications required herein for arbitrators shall be selected pursuant to the
AAA's selection procedures. Judgment upon the decision rendered by a referee
shall be entered in the court in which such proceeding was commenced in
accordance with California Code of Civil Procedure Sections 644 and 645.

        (i) Miscellaneous. To the maximum extent practicable, the AAA, the
arbitrators and the parties shall take all action required to conclude any
arbitration proceeding within 180 days of the filing of the dispute with the
AAA. No arbitrator or other party to an arbitration proceeding may disclose the
existence, content or results thereof, except for disclosures of information by
a party required in the ordinary course of its business or by applicable law or
regulation. If more than one agreement for arbitration by or between the parties
potentially applies to a dispute, the arbitration provision most directly
related to the Loan Documents or the subject matter of the dispute shall
control. This arbitration provision shall survive termination, amendment or
expiration of any of the Loan Documents or any relationship between the parties.

                                      -18-
<PAGE>
        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as of the day and year first written above.

                                              WELLS FARGO BANK,
GEN-PROBE INCORPORATED                          NATIONAL ASSOCIATION

By:                                           By:
   ---------------------------                    ------------------------------
      Henry L. Nordhoff                                  Andrew Andow
      President and Chief Executive Officer              Vice President

By:
   ---------------------------
      Steven R. Martin
      Controller

GEN-PROBE SALES & SERVICE, INC.

By:
   ---------------------------
      Henry L. Nordhoff
      President and Chief Executive Officer

By:
   ---------------------------
      Steven R. Martin
      Controller

                                      -19-<PAGE>
                                                                   EXHIBIT 10.39

                       FIRST AMENDMENT TO CREDIT AGREEMENT

        THIS FIRST AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is entered
into as of June 10, 2002, by and between GEN-PROBE INCORPORATED, a Delaware
corporation and GEN-PROBE SALES & SERVICE, INC., a Delaware corporation
(collectively, "Borrowers" and each, a "Borrower"), and WELLS FARGO BANK,
NATIONAL ASSOCIATION ("Bank").

                                    RECITALS

        WHEREAS, Borrowers are currently indebted to Bank pursuant to the terms
and conditions of that certain Credit Agreement between Borrowers and Bank dated
as of April 10, 2001, as amended from time to time ("Credit Agreement").

        WHEREAS, Bank and Borrowers have agreed to certain changes in the terms
and conditions set forth in the Credit Agreement and have agreed to amend the
Credit Agreement to reflect said changes.

        NOW, THEREFORE, for valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, the parties hereto agree that the Credit
Agreement shall be amended as follows:

        1. Section 1.1.(a) is hereby amended by deleting "July 1, 2002" as the
last day on which Bank will make advances under the Line of Credit, and by
substituting for said date "July 1, 2004," with such change to be effective upon
the execution and delivery to Bank of a promissory note substantially in the
form of EXHIBIT A attached hereto (which promissory note shall replace and be
deemed the Line of Credit Note defined in and made pursuant to the Credit
Agreement) and all other contracts, instruments and documents required by Bank
to evidence such change.

        2. Section 1.1.(c) is hereby renumbered as Section 1.1.(d) and the
following is hereby added to the Credit Agreement as Section 1.1.(c):

                      "(c) Letter of Credit Subfeature. As a subfeature under
               the Line of Credit, Bank agrees from time to time during the term
               thereof to issue or cause an affiliate to issue standby letters
               of credit for the account of Borrowers to finance Borrowers'
               general corporate purposes (each, a "Letter of Credit" and
               collectively, "Letters of Credit"); provided however, that the
               aggregate undrawn amount of all outstanding Letters of Credit
               shall not at any time exceed Five Million Dollars
               ($5,000,000.00). The form and substance of each Letter of Credit
               shall be subject to approval by Bank, in its sole discretion. No
               Letter of Credit shall have an expiration date subsequent to the
               maturity date of the Line of Credit. The undrawn amount of all
               Letters of Credit shall be reserved under the Line of Credit and
               shall not be available for borrowings thereunder. Each Letter of
               Credit shall be subject to the additional terms and conditions of
               the Letter of Credit agreements, applications and any related
               documents required by

                                      -1-
<PAGE>
               Bank in connection with the issuance thereof. Each draft paid
               under a Letter of Credit shall be deemed an advance under the
               Line of Credit and shall be repaid by Borrowers in accordance
               with the terms and conditions of this Agreement applicable to
               such advances; provided however, that if advances under the Line
               of Credit are not available, for any reason, at the time any
               draft is paid, then Borrowers shall immediately pay to Bank the
               full amount of such draft, together with interest thereon from
               the date such draft is paid to the date such amount is fully
               repaid by Borrowers, at the rate of interest applicable to
               advances under the Line of Credit. In such event Borrowers agree
               that Bank, in its sole discretion, may debit any account
               maintained by Borrowers or either of them with Bank for the
               amount of any such draft."

        3. The second paragraph of Section 1.2.(d) (which paragraph begins "Bank
shall adjust") is hereby deleted in its entirety, and the following substituted
therefor:

                      "Bank shall adjust the percentage per annum used to
               determine the amount of the fee on a quarterly basis, commencing
               with Borrowers' fiscal quarter ending June 30, 2002, if required
               to reflect a change in Borrower's ratio of Funded Debt to EBITDA
               (as defined in Section 4.9(e) below), in accordance with the
               following grid:

                      Funded Debt to EBITDA
                      Percentage

                      Less than .75 to 1.0                         .250

                      Greater than or equal to
                      .75                                          .375"

        4. The following is hereby added to the Credit Agreement as Section
1.2.(e):

                      "(e) Letter of Credit Fees. Borrowers shall pay to Bank
               (i) fees upon the issuance of each Letter of Credit equal to one
               and one-half percent (1.5%) per annum (computed on the basis of a
               360-day year, actual days elapsed) of the face amount thereof,
               and (ii) fees upon the payment or negotiation of each draft under
               any Letter of Credit and fees upon the occurrence of any other
               activity with respect to any Letter of Credit (including without
               limitation, the transfer, amendment or cancellation of any Letter
               of Credit) determined in accordance with Bank's standard fees and
               charges then in effect for such activity."

        5. Section 4.9.(d) is hereby deleted, and the following substituted
therefor:

                      "(d) EBITDA not less than $17,000,000.00 as of June 30,
               2002 and September 30, 2002, and not less than $23,000,000.00 as
               of each fiscal quarter end thereafter, calculated on a rolling
               four-quarter basis, with "EBITDA" defined as net profit

                                      -2-
<PAGE>
               before tax plus interest expense (net of capitalized interest
               expense), depreciation expense and amortization expense."

        6. Section 4.9(h) is hereby deleted, and the following substituted
therefor:

                      (h) Net income after taxes not less than $1.00 for the
               fiscal quarter ending December 31, 2001.

                      (i) Net loss after taxes for the fiscal quarter ending
               March 31, 2002, not less than $1,000,000.00.

                      (j) Net loss after taxes for the fiscal quarter ending
               June 30, 2002 not to exceed $1,500,000.00.

                      (k) Net income after taxes not less than $1.00 on a
               quarterly basis determined as of each fiscal quarter end
               commencing with the fiscal quarter ending September 30, 2002. "

        7. The following is hereby added to the Credit Agreement as Section
4.9.(l):

                      "(l) EBITDA Coverage Ratio not less than 2.0 to 1.0 as of
               each fiscal year end, with "EBITDA" as defined above, and with
               "EBITDA Coverage Ratio" defined as EBITDA divided by the
               aggregate of total interest expense plus the prior period current
               maturity of long-term debt and the prior period current maturity
               of subordinated debt."

        8. Section 7.11(c) is hereby deleted and replaced by the following:

                      (c) Each Borrower agrees that it is jointly and severally
               liable to Bank for, and each Borrower agrees to pay to Bank when
               due the full amount of, all indebtedness now existing or
               hereafter arising to Bank under or in connection with the Line of
               Credit and all modifications, extensions and renewals thereof,
               including without limitation all advances disbursed to any
               Borrower under the Line of Credit, all interest which accrues
               thereon, all Letters of Credit issued for the account of any
               Borrower, including without limitation the obligation to
               reimburse Bank for the amount of any draft paid by Bank under any
               such Letter of Credit, together with interest thereon, and all
               fees, costs and expenses chargeable to Borrowers or any of them
               in connection with the Line of Credit. References in the other
               paragraphs of this Section 7.11 to the "Line of Credit" shall
               include, without limitation, the Letter of Credit subfeature
               thereunder."

        9. In consideration of the changes set forth herein and as a condition
to the effectiveness hereof, immediately upon signing this Amendment Borrower
shall pay to Bank a non-refundable fee of $25,000.00.

        10. Except as specifically provided herein, all terms and conditions of
the Credit Agreement remain in full force and effect, without waiver or
modification. All terms defined in the Credit Agreement shall have the same
meaning when used in this Amendment. This Amendment and the Credit Agreement
shall be read together, as one document.

                                      -3-
<PAGE>
        11. Borrower hereby remakes all representations and warranties contained
in the Credit Agreement and reaffirms all covenants set forth therein. Borrower
further certifies that as of the date of this Amendment there exists no Event of
Default as defined in the Credit Agreement, nor any condition, act or event
which with the giving of notice or the passage of time or both would constitute
any such Event of Default.

        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed as of the day and year first written above.

                                                 WELLS FARGO BANK,
GEN-PROBE INCORPORATED                             NATIONAL ASSOCIATION

By:                                              By:
    -------------------------------                  ---------------------------
                                                        Andrew Andow
Title:                                                  Vice President
       ----------------------------

By:
    -------------------------------

Title:
       ----------------------------

GEN-PROBE SALES & SERVICE, INC.

By:
    -------------------------------

Title:
       ----------------------------

By:
    -------------------------------

Title:
       ----------------------------

                                      -4-

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