THIRD AMENDMENT TO CREDIT AGREEMENT


         THIS THIRD AMENDMENT TO CREDIT AGREEMENT (this "Third Amendment") is
entered into as of June 28, 2000 among Covance Inc. (the "Borrower"), certain of
the Borrower's Subsidiaries (individually a "Guarantor" and collectively the
"Guarantors"), the Lenders party to the Credit Agreement defined below (the
"Lenders"), Bank of America, N.A., formerly NationsBank, N.A., as Administrative
Agent (the "Administrative Agent") and Wachovia Bank, N.A., successor by merger
to Wachovia Bank of Georgia, N.A., as Syndication Agent (the "Syndication
Agent"; the Administrative Agent, together with the Syndication Agent, may be
referred to herein as the "Agents"). Capitalized terms used herein and not
otherwise defined herein have the respective meanings given to them in the
Credit Agreement.

                                    RECITALS

         WHEREAS, the Borrower, the Guarantors, the Lenders, the Administrative
Agent and the Syndication Agent are parties to a Credit Agreement dated as of
November 26, 1996 (as previously amended and as further amended, modified,
supplemented or restated from time to time, the "Credit Agreement");

         WHEREAS, the Borrower has requested that the Lenders consent to an
amendment of certain provisions of the Credit Agreement; and

         WHEREAS, the Lenders executing below have agreed to such amendment of
the Credit Agreement on the terms and subject to the conditions contained in
this Third Amendment.

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants herein contained, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

I.       AMENDMENTS

         1.1      All references in the Credit Agreement to NationsBank,
NationsBank, N.A., NationsBanc Capital Markets, Inc. and Wachovia Bank of
Georgia, N.A. shall hereafter refer to Bank of America, Bank of America, N.A.,
Banc of America Securities LLC and Wachovia Bank, N.A., respectively.

         1.2      Section 1.1 of the Credit Agreement is hereby amended by
adding, in appropriate alphabetical order, definitions for the following terms:

                  "ASSET DISPOSITION" means the disposition of any or all of the
         assets of a Credit Party or any of its Subsidiaries whether by sale,
         lease, transfer, condemnation or otherwise, other than sales, leases,
         transfers or other dispositions of assets permitted by Sections 8.5(a)
         - (e).

                  "DIVIDEND RESTRICTED PAYMENT" has the meaning set forth in
         Section 8.8.

                  "FIFTY MILLION CREDIT AGREEMENT" means that certain Credit
         Agreement dated as of June 28, 2000 among the Borrower, the Guarantors,
         the lenders party thereto and Bank of America, N.A., as administrative
         agent, as such Credit Agreement may be amended, modified, supplemented,
         extended or restated from time to time.

                  "FMCA REVOLVING COMMITTED AMOUNT" means the "Revolving
         Committed Amount" as defined from time to time in the Fifty Million
         Credit Agreement.

                  "INTERCREDITOR AGREEMENT" means that certain Intercreditor
         Agreement dated as of June 28, 2000 by and among Bank of America, as
         Administrative Agent under this Credit Agreement, Bank of America, as
         administrative agent under the Fifty Million Credit Agreement, and the
         Credit Parties, as amended, modified, supplemented or restated from
         time to time, in substantially the form of EXHIBIT 10.10.

                  "NET CASH PROCEEDS" means the aggregate amount of all proceeds
         paid in cash or Cash Equivalents received by any Credit Party in
         respect of any Asset Disposition (but with respect to any payments
         received by way of deferred payment of principal pursuant to a note or
         installment receivable or purchase price adjustment receivable or
         otherwise, only as and when received), net of (a) all fees and expenses
         (including, without limitation, investment banking fees, legal and
         accounting fees, sales commissions and brokerage commissions) incurred
         in connection with such Asset Disposition, (b) taxes paid or payable in
         connection with or as a result thereof and (c) any repayments of
         Indebtedness permitted by Section 8.1 (other than Borrower

<PAGE>
         Obligations) to extent such repayments are required by the terms of the
         debt instrument governing such Indebtedness in connection with such
         Asset Disposition; it being understood that "Net Cash Proceeds" shall
         include, without limitation, any cash or Cash Equivalents received upon
         the sale or other disposition of any non-cash consideration received by
         a Credit Party in respect of any Asset Disposition

                  "PRO FORMA BASIS" means, for purposes of calculating the
         Leverage Ratio to determine compliance with the terms of Section 8.8,
         that any reduction of the Revolving Committed Amount (and corresponding
         prepayment of Loans) shall be deemed to have occurred as of the first
         day of the four fiscal-quarter period ending as of the last day of the
         most recently completed fiscal quarter preceding the date of such
         reduction (and prepayment) with respect to which the Administrative
         Agent and the Lenders have received the officer's certificate required
         to be delivered pursuant to Section 7.1(c).

                  "QUOTATION DAY" means (a) if the Loan is made in Dollars or
         any Foreign Currency other than Euro, two Business Days prior to the
         first day of such Interest Period and (b) if the Loan is made in Euro,
         two TARGET Days prior to the first day of such Interest Period;
         provided that if market practice differs in the Relevant Interbank
         Market for a Foreign Currency, then the Quotation Day for that Foreign
         Currency will be determined by the Administrative Agent in accordance
         with market practice in the Relevant Interbank Market (and if
         quotations would normally be given by leading banks in the Relevant
         Interbank Market on more than one day, the Quotation Day will be the
         last of those days).

                  "RELEVANT INTERBANK MARKET" means the market in which a London
         Interbank Offered Rate for the applicable Interest Period is available
         in immediately available funds in the applicable Foreign Currency.

                  "STOCK REPURCHASE RESTRICTED PAYMENT" has the meaning set
         forth in Section 8.8.

                  "TARGET" means Trans-European Automated Real-time Gross
         Settlement Express Transfer payment system.

                  "TARGET DAY" means any day on which TARGET is open for the
         settlement of payments in Euro.

         1.3      The definition of "ADJUSTED LEVERAGE RATIO" in Section 1.1 of
the Credit Agreement is hereby deleted.

         1.4      The definition of "APPLICABLE PERCENTAGE" in Section 1.1 of
the Credit Agreement is hereby amended and restated in its entirety to read as
follows:

                  "APPLICABLE PERCENTAGE" means (a) for Eurocurrency Loans and
         Letter of Credit Fees, 1.25% and (b) for Facility Fees, 0.25%.

         1.5      The definition of "BENEFITS PLAN" in Section 1.1 of the Credit
Agreement is hereby amended and restated in its entirety to read as follows:

                  "BENEFITS PLAN" means each of (a) the Employee Stock Ownership
         Plan of the Borrower, (b) the Trust Deed of the Covance Inc. Employee
         Share Trust between the trustee and the Borrower, (c) the Stock
         Purchase Savings Plan of the Borrower restated as of December 31, 1996,
         (d) the Employee Stock Purchase Plan of the Borrower, (e) the Employee
         Equity Participation Program of the Borrower and the 2000 Employee
         Equity Participation Program of the Borrower and (f) any other "pension
         plan" (as defined in Section 3(2) of ERISA) of the Borrower or trust
         created thereunder.

         1.6      The definition of "CREDIT DOCUMENTS" in Section 1.1 of the
Credit Agreement is hereby amended and restated in its entirety to read as
follows:

                  "CREDIT DOCUMENTS" means this Credit Agreement, the Notes, any
         Joinder Agreement, the Fee Letter, the Collateral Documents, the
         Intercreditor Agreement and all other related agreements and documents
         issued or delivered hereunder by (i) a Guarantor to guarantee the
         Borrower Obligations or to secure such guarantee or (ii) the Borrower
         or one of its Subsidiaries (other than a Guarantor) to secure the
         Borrower Obligations.

                                       2
<PAGE>
         1.7      The definition of "EBIT" in Section 1.1 of the Credit
Agreement is hereby amended and restated in its entirety to read as follows:

                  "EBIT" means, for any period, with respect to the Borrower and
         its Subsidiaries on a consolidated basis, the sum of (a) Net Income for
         such period (excluding the effect of any extraordinary or other
         non-recurring gains or losses outside of the ordinary course of
         business); provided that for the fiscal quarter ending June 30, 2000,
         Net Income shall not include a one time restructuring charge not to
         exceed $16,500,000, PLUS (b) an amount which, in the determination of
         Net Income for such period, has been deducted for (i) Interest Expense
         for such period and (ii) total Federal, state, foreign or other income
         taxes for such period, all as determined in accordance with GAAP.

         1.8      The definition of "FOREIGN CURRENCY" in Section 1.1 of the
Credit Agreement is hereby amended and restated in its entirety to read as
follows:

                  "FOREIGN CURRENCY" means British Pounds Sterling, Japanese Yen
         and the Euro or such other currency as agreed to between the Borrower
         and all the Lenders. Each Foreign Currency must be one (a) that is
         readily available to the Lenders and freely transferable and
         convertible into Dollars and (b) in which deposits are generally
         available to the Lenders in the London interbank market.

         1.9      The definition of "GUARANTOR" in Section 1.1 of the Credit
Agreement is hereby amended and restated in its entirety to read as follows:

                  "GUARANTOR" means at any time, (a) each of the parties to this
         Credit Agreement listed as "Guarantors" on the signature pages hereof
         (which are the only Material Domestic Subsidiaries as of the Closing
         Date) and (b) each other Person that is an Additional Credit Party, in
         each case, together with their successors and assigns, but excluding
         any such Person that shall have been released from its Guaranty
         Obligations pursuant to Section 4.9, Section 7.12 or Section 7.15.

         1.10     The definition of "LONDON INTERBANK OFFERED RATE" in Section
1.1 of the Credit Agreement is hereby amended and restated in its entirety to
read as follows:

                  "LONDON INTERBANK OFFERED RATE" means, with respect to any
         Eurocurrency Loan for the Interest Period applicable thereto, the rate
         of interest per annum (rounded upwards, if necessary, to the nearest
         1/100 of 1%) appearing on Telerate Page 3750 or such other applicable
         page (or any successor page) as the London interbank offered rate for
         deposits in Dollars (or the applicable Foreign Currency) at
         approximately 11:00 A.M. (London time) on the Quotation Day for a term
         comparable to such Interest Period; provided, however, if more than one
         rate is specified on Telerate Page 3750, or such other applicable page,
         the applicable rate shall be the arithmetic mean of all such rates. If,
         for any reason, such rate is not available, the term "LONDON INTERBANK
         OFFERED RATE" shall mean, with respect to any Eurocurrency Loan for the
         Interest Period applicable thereto, the rate of interest per annum
         (rounded upwards, if necessary, to the nearest 1/100 of 1%) appearing
         on Reuters Screen LIBO Page as the London interbank offered rate for
         deposits in Dollars (or the applicable Foreign Currency) at
         approximately 11:00 A.M. (London time) on the Quotation Day for a term
         comparable to such Interest Period; provided, however, if more than one
         rate is specified on Reuters Screen LIBO Page, the applicable rate
         shall be the arithmetic mean of all such rates.

         1.11     The definition of "MATERIAL ADVERSE EFFECT" in Section 1.1 of
the Credit Agreement is hereby amended and restated in its entirety to read as
follows:

                  "MATERIAL ADVERSE EFFECT" means a material adverse effect
         (after giving effect to any insurance proceeds or indemnification
         payments under existing insurance policies or agreements as long as the
         carrier of such policies or agreements has acknowledged coverage) on
         (a) the results of operations or financial condition of the Borrower
         and its Subsidiaries taken as a whole, (b) the ability of a Credit
         Party to perform its respective obligations under this Credit Agreement
         or any of the other Credit Documents, or (c) the validity or
         enforceability of this Credit Agreement, any of the other Credit
         Documents, or the rights and remedies of the Lenders hereunder or
         thereunder taken as a whole; provided, however, (i) the execution,
         delivery and performance of the Credit Documents shall not constitute
         an Material Adverse Effect and (ii) a one time restructuring charge in
         an amount not to exceed $16,500,000 taken by the Borrower during the
         fiscal quarter ending June 30, 2000 shall not constitute a Material
         Adverse Effect.

                                       3
<PAGE>
         1.12     The definition of "PERMITTED LIENS" in Section 1.1 of the
Credit Agreement is hereby amended by adding the following subsection (u) and by
making the appropriate grammatical and punctuation changes:

                           (u) Liens arising pursuant to and in connection with
                  Indebtedness permitted by Section 8.1(j); it being understood
                  and agreed that such Liens shall rank pari passu with the
                  Liens securing the Credit Party Obligations pursuant to the
                  Collateral Documents in accordance with the terms of the
                  Intercreditor Agreement.

         1.13     The definition of "U.S. DOLLAR EQUIVALENT" in Section 1.1 of
the Credit Agreement is hereby amended and restated in its entirety to read as
follows:

                  "U.S. DOLLAR EQUIVALENT" means the amount of Dollars that
         would be realized by converting a Foreign Currency into Dollars at
         approximately 11:00 a.m. (London time), as set forth on the applicable
         Telerate Screen, on the date of determination; provided that if more
         than one rate is listed then the applicable conversion rate shall be
         the arithmetic average of such rates. If for any reason such conversion
         rates are not available, the U.S. Dollar Equivalent shall be calculated
         using the arithmetic average of the spot buying rates for such Foreign
         Currency in Dollars as quoted to the Administrative Agent by three
         foreign exchange dealers of recognized standing in the United States
         selected by the Administrative Agent at approximately 11:00 a.m.
         (London time) on any date of determination.

         1.14     Section 2.1(d) of the Credit Agreement is hereby amended and
restated in its entirety to read as follows:

                  (d) REDUCTIONS OF REVOLVING COMMITTED AMOUNT. Upon at least
         three Business Days' notice, the Borrower shall have the right to
         permanently terminate or reduce the aggregate unused amount of the
         Revolving Committed Amount at any time or from time to time; provided
         that (i) each partial reduction shall be in an aggregate amount at
         least equal to $5,000,000 and in integral multiples of $1,000,000 above
         such amount and (ii) no reduction shall be made which would reduce the
         Revolving Committed Amount to an amount less than the aggregate amount
         of outstanding Revolving Loans plus the aggregate amount of outstanding
         LOC Obligations plus the aggregate amount of Swing Line Loans
         outstanding plus the aggregate amount of Competitive Bid Loans
         outstanding. The Revolving Committed Amount shall be reduced pursuant
         to the terms of Section 3.3(b)(ii). Any reduction in (or termination
         of) the Revolving Committed Amount shall be permanent and may not be
         reinstated. The Administrative Agent shall immediately notify the
         Lenders of any reduction in the Revolving Committed Amount.

         1.15     Section 2.2(g) of the Credit Agreement is hereby amended and
restated in its entirety to read as follows:

                  (g) UNIFORM CUSTOMS AND PRACTICES. The Issuing Lender may have
         the Letters of Credit be subject to The Uniform Customs and Practice
         for Documentary Credits or the International Standby Practices 1998
         (the "ISP98"), in either case as published as of the date of issue by
         the International Chamber of Commerce, in which case the UCP or the
         ISP98, as applicable, may be incorporated therein and deemed in all
         respects to be a part thereof.

         1.16     Section 2.2(j)(v) of the Credit Agreement is hereby amended by
inserting a comma and the term "ISP98" after the term "UCP" in the eighth line
thereof.

         1.17     Sections 3.3(b) and (c) of the Credit Agreement are hereby
amended and restated in their entirety to read as follows:

                  (b)      MANDATORY PREPAYMENTS.

                           (i) AVAILABILITY. If at any time (A) the sum of the
                  aggregate amount of Revolving Loans outstanding plus the
                  aggregate amount of Swing Line Loans outstanding plus the
                  aggregate amount of Competitive Bid Loans outstanding plus the
                  aggregate amount of LOC Obligations outstanding exceeds the
                  Revolving Committed Amount, (B) the aggregate amount of Swing
                  Line Loans outstanding exceeds the Swing Line Committed
                  Amount, (C) the aggregate amount of LOC Obligations
                  outstanding exceeds the LOC Committed Amount, or (D) the
                  aggregate amount of Revolving Loans outstanding in Foreign
                  Currency plus the aggregate amount of LOC Obligations
                  outstanding in Foreign Currency plus the aggregate amount of
                  Competitive Bid Loans outstanding in Foreign Currency exceeds
                  the U.S. Dollar Equivalent of Fifty Million Dollars
                  ($50,000,000), the Borrower shall immediately make a principal
                  payment to the Administrative Agent in the manner and in an
                  amount necessary to be in compliance with Sections 2.1, 2.2,
                  2.3 or 2.4, as applicable.

                                       4
<PAGE>
                           (ii) ASSET DISPOSITIONS. Within two Business Days
                  after the closing of any Asset Disposition, (A) the Borrower
                  shall prepay the Loans and the loans outstanding under the
                  Fifty Million Credit Agreement, on a pro rata basis
                  (determined based on the amounts outstanding thereunder on the
                  date of such Asset Disposition), in an aggregate amount equal
                  to 50% of the Net Cash Proceeds of such Asset Disposition and
                  (B) the Revolving Committed Amount and the FMCA Revolving
                  Committed Amount shall be reduced, on a pro rata basis, by an
                  aggregate amount equal to 50% of the Net Cash Proceeds of such
                  Asset Disposition.

                  (c) APPLICATION OF PREPAYMENTS. All amounts required to be
         paid pursuant to Section 3.3(b)(i)(A) or 3.3(b)(ii) shall be applied
         FIRST to Revolving Loans (first to Base Rate Loans and then to
         Eurocurrency Loans in direct order of Interest Period maturities),
         SECOND to Swing Line Loans (first to Base Rate Loans and then to Quoted
         Rate Swing Line Loans), THIRD to a cash collateral account in respect
         of LOC Obligations and FOURTH to Competitive Bid Loans pro rata among
         the Lenders holding same. All amounts required to be paid pursuant to
         Section 3.3(b)(i)(B) shall be applied to Swing Line Loans (first to
         Base Rate Loans and then to Quoted Rate Swing Line Loans). All amounts
         required to be paid pursuant to Section 3.3(b)(i)(C) shall be paid to a
         cash collateral account in respect of LOC Obligations. All amounts
         required to be paid pursuant to Section 3.3(b)(i)(D) shall be applied
         FIRST to Revolving Loans outstanding in Foreign Currency (first to Base
         Rate Loans (if any) and then to Eurocurrency Loans in direct order of
         Interest Period maturities), SECOND to a cash collateral account in
         respect of LOC Obligations outstanding in Foreign Currency and THIRD to
         Competitive Bid Loans outstanding in Foreign Currency pro rata among
         the Lenders holding same. All prepayments hereunder shall be subject to
         Section 3.14 as well as any breakage fees in connection with a
         prepayment of a Competitive Bid Loan or a Quoted Rate Swing Line Loan
         and shall be accompanied by interest on the principal amount prepaid
         through the date of prepayment.

         1.18     A new Section 4.9 is hereby added to the Credit Agreement and
reads as follows:

         4.9      RELEASE OF GUARANTOR. If any of the Guarantors shall cease to
be a Subsidiary of the Borrower for any reason subject to and in accordance with
the terms of the Credit Agreement, then such Guarantor shall, automatically and
without any further action on the part of any party to any Credit Document, and
upon notice to the Administrative Agent, be fully released and discharged from
all its liabilities and obligations under or in respect of the Credit Documents
to which such Guarantor is a party (other than liabilities and obligations
resulting from a demand on such Guarantor's Guaranty pursuant to Section 9.2)
and, promptly upon the request of the Borrower and at the expense of the
Borrower, the Administrative Agent shall execute such documents and take such
other action as is reasonably requested by the Borrower to evidence the release
and discharge of such Guarantor from all such liabilities and obligations and
shall, if applicable, certify to the Borrower that such Guarantor has no
liabilities or obligations resulting from a demand on such Guarantor's Guaranty
pursuant to Section 9.2.

         In the event the Borrower or any of its Subsidiaries intends to sell,
transfer or otherwise dispose of the capital stock of any Subsidiary (subject to
and in accordance with the terms of the Credit Agreement) whose capital stock
has been pledged and delivered to the Administrative Agent pursuant to a Pledge
Agreement, upon notice thereof to the Administrative Agent, the Administrative
Agent shall promptly deliver to the Borrower such capital stock (pursuant to an
escrow arrangement acceptable to the Administrative Agent), and, effective upon
such sale, transfer or disposition, the Liens imposed by or under the Credit
Agreement and the Pledge Agreement on such capital stock shall automatically and
without any further action on the part of any party to any Credit Documents, be
fully released and discharged. Promptly upon the request of the Borrower and at
the expense of the Borrower, the Administrative Agent shall execute such
documents and take such other actions as is reasonably requested by the Borrower
to evidence the release and discharge of any such Lien.

         In the event the Borrower or any of its Subsidiaries intends to sell,
transfer or otherwise dispose of the capital stock of any Guarantor (subject to
and in accordance with the terms of the Credit Agreement) which has executed and
delivered a Collateral Assignment of Notes to the Administrative Agent, upon
notice thereof to the Administrative Agent, the Administrative Agent shall
promptly deliver to the Borrower the applicable promissory notes (pursuant to an
escrow arrangement acceptable to the Administrative Agent), and, effective upon
such sale, transfer or disposition, the Liens imposed by or under the Credit
Agreement and the Collateral Assignment of Notes on such notes shall
automatically and without any further action on the part of any party to any
Credit Documents, be fully released and discharged. Promptly upon the request of
the Borrower and at the expense of the Borrower, the Administrative Agent shall
execute such documents and take such other actions as is reasonably requested by
the Borrower to evidence the release and discharge of any such Lien.

         To the extent any of the provisions of this Section 4.9 are
inconsistent with any of the provisions of Section 7.12 or Section 7.15, the
provisions of this Section 4.9 shall govern.

                                       5
<PAGE>
         1.19     Section 7.1(c)(i) of the Credit Agreement is hereby amended by
deleting the phrase "and showing the calculation of the Adjusted Leverage Ratio
for purposes of determining Applicable Percentage" set forth therein.

         1.20     Sections 7.2 of the Credit Agreement is hereby amended and
restated in its entirety to read as follows:

         7.2      FINANCIAL COVENANTS.

                  (a)      LEVERAGE RATIO. The Leverage Ratio, as of the end of
         each fiscal quarter of the Borrower for the twelve month period ending
         on such date, shall be less than or equal to:

                           (i)      On June 30, 2000 and September 30, 2000, 3.0
                  to 1.0; and

                           (ii)     On December 31, 2000 and on the last day of
                  each fiscal quarter of the Borrower thereafter, 2.75 to 1.0.

                  (b)      FIXED CHARGE COVERAGE RATIO. The Fixed Charge
         Coverage Ratio, as of the end of each fiscal quarter of the Borrower
         for the twelve month period ending on such date, shall be greater than
         or equal to:

                           (i)      On June 30, 2000 and September 30, 2000, 2.0
                  to 1.0; and

                           (ii)     On December 31, 2000 and on the last day of
                  each fiscal quarter of the Borrower thereafter, 2.25 to 1.0.

         1.21     Section 8.1 of the Credit Agreement is hereby amended by
adding the following subsections (j) and (k) and by making the appropriate
grammatical and punctuation changes:

                  (j) Indebtedness arising under the Fifty Million Credit
         Agreement in a principal amount not to exceed $50,000,000 (and
         renewals, refinancings or extensions thereof on terms and conditions
         substantially the same as such Indebtedness and in a principal amount
         not in excess of that outstanding as of the date of such renewal,
         refinancing or extension); and

                  (k) Indebtedness consisting of any synthetic lease, tax
         retention operating lease, off-balance sheet loan or similar
         off-balance sheet financing product where such transaction is
         considered borrowed money indebtedness for tax purposes but is
         classified as an operating lease in accordance with GAAP, the principal
         amount of such Indebtedness not to exceed $35,000,000 in the aggregate.

         1.22     Section 8.5 of the Credit Agreement is hereby amended and
restated in its entirety to read as follows:

         8.5      SALE OR LEASE OF ASSETS.

         No Credit Party will, nor will it permit any of its Subsidiaries to,
convey, sell, lease, transfer or otherwise dispose of, in one transaction or a
series of transactions, all or any part of its business or assets whether now
owned or hereafter acquired, including, without limitation, inventory,
receivables, equipment, real property interests (whether owned or leasehold),
and securities, other than (a) any inventory sold or otherwise disposed of in
the ordinary course of business; (b) the sale, lease, transfer or other disposal
by a Credit Party (other than the Borrower) of any or all of its assets to the
Borrower or to another Credit Party; (c) obsolete, slow-moving, idle or worn-out
assets (including inventory) no longer used or useful in its business; (d) the
transfer of assets which constitute a Permitted Investment; (e) the lease of
assets as provided in the Lease; or (f) such other transfer of assets if (i)
such transfer is for fair market value, (ii) at the time of such transfer no
Default or Event of Default exists and is continuing, (iii) as a result of such
transfer no Material Adverse Effect would occur or be reasonably likely to
occur, (iv) 50% of the Net Cash Proceeds from such transfer are used to prepay
Loans in accordance with the terms of Section 3.3(b)(ii), and (v) the balance of
the Net Cash Proceeds from such transfer (A) are used to prepay Loans, (B) are
used to make Stock Repurchase Restricted Payments subject to and in accordance
with the terms of Section 8.8 or (C) are reinvested in a business of a type
similar to that which the Credit Parties and their Subsidiaries are already
engaged or were engaged at the time of such transfer.

                                       6
<PAGE>
         1.23     Section 8.8 of the Credit Agreement is hereby amended and
restated in its entirety to read as follows:

         8.8      RESTRICTED PAYMENTS.

         No Credit Party will, directly or indirectly, nor will it permit its
Subsidiaries to, (a) declare or pay any dividends or make any other distribution
upon any shares of its capital stock of any class (each such dividend or
distribution a "Dividend Restricted Payment") or (b) purchase, redeem or
otherwise acquire or retire or make any provisions for redemption, acquisition
or retirement of any shares of its capital stock of any class or any warrants or
options to purchase any such shares (each such, repurchase, redemption,
acquisition or retirement a "Stock Repurchase Restricted Payment"); provided
that (i) any Subsidiary of the Borrower may make Dividend Restricted Payments or
Stock Repurchase Restricted Payments to the Borrower or a Guarantor, (ii)
Dividend Restricted Payments in the form of stock may be paid pursuant to the
Rights Plan and the Benefits Plans, (iii) as long as no Default or Event of
Default exists and is continuing, Dividend Restricted Payments may be made with
respect to (A) the Benefits Plans of the type referred to in subsection (a) and
(b) of the definition of "Benefits Plans", (B) the Benefits Plans of the type
referred to in subsection (c), (d), (e) and (f) of the definition of "Benefits
Plans" in an aggregate amount not to exceed $50,000,000 during the term of this
Credit Agreement and (C) the Rights Plans in an aggregate amount not to exceed
$2,000,000 during the term of this Credit Agreement, (iv) other than with
proceeds from a sale, lease, transfer or other disposition of assets or a
business permitted by Section 8.5, Dividend Restricted Payments may be made (A)
if no Default or Event of Default exists and is continuing and (B) if after
giving effect thereto, the Credit Parties and their Subsidiaries are in
compliance with Section 7.2 and (v) the Credit Parties shall be entitled to make
Stock Repurchase Restricted Payments if (A) the Leverage Ratio, as determined on
a Pro Forma Basis, is less than or equal to 1.5 to 1.0, (B) the Revolving
Committed Amount hereunder and the FMCA Revolving Committed Amount have been
permanently reduced to $150,000,000 or less in the aggregate, and (C) the
Borrower delivers to the Administrative Agent and the Lenders an officer's
certificate demonstrating compliance with the foregoing clauses (v)(A) and
(v)(B). The aggregate amount of all Stock Repurchase Restricted Payments after
June 30, 2000 shall not exceed $75,000,000.

         1.24     Section 9.1 of the Credit Agreement is hereby amended by
adding the following subsection (k) to read as follows:

                  (k)      FIFTY MILLION CREDIT AGREEMENT. There shall occur an
         Event of Default (as defined in the Fifty Million Credit Agreement)
         under the Fifty Million Credit Agreement.

         1.25     A new Section 10.10 is hereby added to the Credit Agreement to
read as follows:

         10.10    INTERCREDITOR AGREEMENT.

         The Lenders and the Agents acknowledge and agree that the collateral
pledged to the Administrative Agent, on behalf of the Lenders, by the Credit
Parties pursuant to the Collateral Documents shall also secure the obligations
of the Credit Parties under the Fifty Million Credit Agreement and that the
Liens granted by the Credit Parties pursuant to the Collateral Documents and the
Liens granted by the Credit Parties in connection with the Fifty Million Credit
Agreement shall rank pari passu. By execution hereof, each Lender hereby
acknowledges and agrees to be bound by the terms of the Intercreditor Agreement
and further authorizes and directs the Administrative Agent to enter into the
Intercreditor Agreement on its behalf.

         1.26     A new EXHIBIT 10.10 is hereby added to the Credit Agreement in
the form of EXHIBIT 10.10 attached hereto.

II.      CONDITIONS PRECEDENT

         2.1      This Third Amendment shall be effective upon receipt by the
Administrative Agent of each of the following:

                  (a)      Counterparts of this Third Amendment duly executed by
         the Credit Parties and the Required Lenders;

                  (b)      An amendment fee, for the benefit of each Lender that
         approves, executes and delivers to the Administrative Agent this Third
         Amendment prior to the effectiveness hereof, equal to 0.25% of the
         Commitment of such Lender;

                                       7
<PAGE>
                  (c)      Copies of resolutions of the Board of Directors of
         each Credit Party (or its general partner, as applicable) approving and
         adopting this Third Amendment, the transactions contemplated herein and
         authorizing execution and delivery hereof, certified by a secretary or
         assistant secretary of such Credit Party (or its general partner, as
         applicable) to be true and correct and in force and effect as of the
         date hereof; and

                  (d)      An opinion from legal counsel to the Credit Parties
         (which shall cover, among other things, authority, legality, validity,
         binding effect and enforceability), reasonably satisfactory to the
         Administrative Agent, addressed to the Agents and the Lenders and dated
         as of the date hereof.

III.     MISCELLANEOUS

         3.1      The term "Credit Agreement" as used in each of the Credit
Documents shall hereafter mean the Credit Agreement as amended by this Third
Amendment. Except as herein specifically agreed, the Credit Agreement is hereby
ratified and confirmed and shall remain in full force and effect according to
its terms.

         3.2      Each of the Credit Parties represents and warrants as follows:

                  (a)      It has taken all necessary action to authorize the
         execution, delivery and performance of this Third Amendment.

                  (b)      This Third Amendment has been duly executed and
         delivered by such Credit Party and constitutes such Credit Party's
         legal, valid and binding obligations, enforceable in accordance with
         its terms, except as such enforceability may be subject to (i)
         bankruptcy, insolvency, reorganization, fraudulent conveyance or
         transfer, moratorium or similar laws affecting creditors' rights
         generally and (ii) general principles of equity (regardless of whether
         such enforceability is considered in a proceeding at law or in equity).

                  (c)      No consent, approval, authorization or order of, or
         filing, registration or qualification with, any court or governmental
         authority or third party is required in connection with the execution,
         delivery or performance by such Credit Party of this Third Amendment.

                  (d)      The representations and warranties of such Credit
         Party set forth in Section 6 of the Credit Agreement are true and
         correct in all material respects as of the date hereof except to the
         extent they expressly relate to an earlier date.

                  (e)      No Default or Event of Default exists and is
         continuing.

         3.3      This Third Amendment shall constitute a Credit Document.

         3.4      The Guarantors acknowledge and consent to all of the terms and
conditions of this Third Amendment and agree that this Third Amendment and all
documents executed in connection herewith do not operate to reduce or discharge
the Guarantors' obligations under the Credit Documents.

         3.5      This Third Amendment may be executed in any number of
counterparts, each of which when so executed and delivered shall be an original,
but all of which shall constitute one and the same instrument.

         3.6      THIS THIRD AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE
PARTIES HEREUNDER SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
OF THE STATE OF NEW YORK.

                                       8
<PAGE>
         IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this Third Amendment to be duly executed and delivered by their proper and
duly authorized officer as of the day and year first above written.

BORROWER:
                               COVANCE INC.,
                               a Delaware corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

GUARANTORS:                    COVANCE PERIAPPROVAL SERVICES INC.,
                               a Delaware corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               COVANCE PHARMACEUTICAL PACKAGING
                               SERVICES INC., a Pennsylvania corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               COVANCE LABORATORIES INC.,
                               a Delaware corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------


                               COVANCE RESEARCH PRODUCTS INC.,
                               a Pennsylvania corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               COVANCE CENTRAL LABORATORY SERVICES
                               LIMITED PARTNERSHIP, AN INDIANA LIMITED
                               PARTNERSHIP

                               By Covance Central Laboratory Services Inc., a
                               Delaware corporation, its General Partner

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------
<PAGE>
                               COVANCE PRECLINICAL CORPORATION,
                               a Washington corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               COVANCE CENTRAL LABORATORY SERVICES
                               INC., a Delaware corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               CJB INC.,
                               a Delaware corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               COVANCE BIOTECHNOLOGY SERVICES INC.,
                               a Delaware corporation

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

AGENTS:

                               BANK OF AMERICA, N.A.,
                               formerly NationsBank, N.A., in its capacity as
                               Administrative Agent and as a Lender

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               WACHOVIA BANK, N.A.,
                               Successor by merger to Wachovia Bank of Georgia,
                               N.A., in its capacity as Syndication Agent and
                               as a Lender

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------
<PAGE>
LENDERS:
                               BANK OF MONTREAL

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               THE FUJI BANK, LIMITED

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               MORGAN GUARANTY TRUST COMPANY
                               OF NEW YORK

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               BANK OF NOVA SCOTIA

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               PARIBAS, F/K/A BANQUE PARIBAS

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               BARCLAYS BANK PLC

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               THE CHASE MANHATTAN BANK

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------
<PAGE>
                               CREDIT SUISSE FIRST BOSTON

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               THE DAI-ICHI KANGYO BANK, LTD.

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               FLEET NATIONAL BANK

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               BANK OF TOKYO - MITSUBISHI TRUST
                               COMPANY

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               MELLON BANK, N.A.

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               PNC BANK, NATIONAL ASSOCIATION

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------

                               THE SANWA BANK LTD.

                               By:
                                  -----------------------------------------
                               Name:
                                    ---------------------------------------
                               Title:
                                     --------------------------------------