Exhibit 10.1


                       FIRST AMENDMENT TO CREDIT AGREEMENT


         This FIRST AMENDMENT TO TERM LOAN CREDIT AGREEMENT (this "Amendment")
is entered into as of April 20, 2004 among QUEST DIAGNOSTICS INCORPORATED, a
Delaware corporation (the "Borrower"), certain Subsidiaries of the Borrower, as
Guarantors (the "Guarantors"), the Lenders party hereto and Sumitomo Mitsui
Banking Corporation, as Administrative Agent for the Lenders (the
"Administrative Agent"). Capitalized terms used herein and not otherwise defined
shall have the meanings set forth in the Credit Agreement (as defined below).

                                    RECITALS

         WHEREAS, the Borrower, the Guarantors, the Lenders and the
Administrative Agent entered into that certain Term Loan Credit Agreement dated
as of December 19, 2003, as amended hereby and as the same may hereafter be
further amended, modified, supplemented or restated, the "Credit Agreement");

         WHEREAS, the Credit Agreement incorporated in Section 7 of the Credit
Agreement the corresponding covenants contained in Section 7 of the Credit
Agreement dated as of June 27, 2001, (the "2001 Senior Credit Agreement") among
the Borrower, the Guarantors, the lender parties thereto and Bank of America,
N.A., as Administrative Agent entered into a Credit Agreement dated as of June
27, 2001, (the "2001 Senior Credit Agreement").

         WHEREAS, Section 11.6 of the Credit Agreement provides that if the
Initial Lender participates in a facility that replaces the 2001 Senior Credit
Agreement (a "Replacement Facility"), such participation shall represent its
agreement to amend the Credit Agreement to conform to the covenants of such
Replacement Facility without payment of any fees in connection with such
confirming amendment.

         WHEREAS, subsequent to the execution of the Credit Agreement, the 2001
Senior Credit Agreement was replaced by a Credit Agreement dated as of April 20,
2004 (the "2004 Senior Credit Agreement") among Borrower, the Guarantors, the
lender parties thereto (including the Initial Lender) and Bank of America, N.A.,
as Administrative Agent.

         WHEREAS, the Initial Lender was a lender party to the 2004 Senior
Credit Agreement, which constitutes a Replacement Facility for purposes of
Section 11.6 of the Credit Agreement.

         WHEREAS, the Credit Parties are requesting that the Lenders agree to
amend certain terms of the Credit Agreement in order to conform certain of the
covenants to those contained in the 2004 Senior Credit Agreement; and

         WHEREAS, the Lenders have agreed to such amendments, subject to the
conditions set forth below.








         NOW THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:


                                    AGREEMENT

         1. Amendments to Credit Agreement.

                  (a) Existing Definitions. The following definitions set forth
         in Section 1.1 of the Credit Agreement are amended and restated in
         their entirety to read as follows:

                  "Cash Equivalents" means (a) securities issued or directly and
         fully guaranteed or insured by the United States of America or any
         agency or instrumentality thereof having maturities of not more than
         eighteen months from the date of acquisition, (b) Dollar denominated
         time and demand deposits, certificates of deposit and banker's
         acceptances of (i) any Lender, (ii) any domestic commercial bank having
         capital and surplus in excess of $500,000,000 or (iii) any bank whose
         short-term commercial paper rating from S&P is at least A-1 or the
         equivalent thereof or from Moody's is at least P-1 or the equivalent
         thereof (any such bank being an "Approved Bank"), in each case with
         maturities of not more than 270 days from the date of acquisition, (c)
         commercial paper and variable or fixed rate notes issued by any
         Approved Bank (or by the parent company thereof) or any variable rate
         notes issued by, or guaranteed by, any domestic corporation rated A-1
         (or the equivalent thereof) or better by S&P or P-1 (or the equivalent
         thereof) or better by Moody's and maturing within six months of the
         date of acquisition, (d) repurchase agreements with a bank or trust
         company (including any of the Lenders) or recognized securities dealer
         having capital and surplus in excess of $500,000,000 for direct
         obligations issued by or fully guaranteed by the United States of
         America in which the Borrower shall have a perfected first priority
         security interest (subject to no other Liens) and having, on the date
         of purchase thereof, a fair market value of at least 100% of the amount
         of the repurchase obligations, (e) Investments in tax-exempt municipal
         bonds rated A (or the equivalent thereof) or better by S&P or MIG2 (or
         the equivalent thereof) or better by Moody's, (f) auction rate
         securities rated AA or better by S&P or Moody's, in either case with a
         reset of no longer than 90 days and (g) Investments, classified in
         accordance with GAAP as current assets, in money market investment
         programs registered under the Investment Company Act of 1940, as
         amended, which are administered by reputable financial institutions
         having capital of at least $500,000,000 and the portfolios of which are
         limited to Investments of the character described in the foregoing
         subdivisions (a) through (f).

                  "EBITDA" means, for any period, with respect to the Borrower
         and its Subsidiaries on a consolidated basis, (a) Net Income for such
         period (excluding the effect of any extraordinary or other
         non-recurring gains and losses (including any gain or loss from the
         sale of Property)) plus (b) an amount which, in the determination of
         Net Income for such period, has been deducted for (i) Interest Expense
         for such period, (ii) total Federal, state, foreign or other income or
         franchise taxes for such period, (iii) all depreciation and
         amortization for such period, (iv) other items of expense during such
         period that do not involve a cash payment at any time (other than the
         provision for bad



                                       2







         debt in connection with uncollectible accounts receivable), (v) cash
         charges during such period for which the Borrower and its Subsidiaries
         are reimbursed by a third party during such period and (vi) special or
         restructuring items during any such period included in Net Income that
         do not involve a cash payment during such period (collectively,
         "Non-Cash Items") minus (c) any actual cash payments during the
         applicable period related to Non-Cash Items expensed or reserved under
         clauses (v) and (vi) above plus (d) Tender Costs during such period.

                  "Eligible Assets" means any assets or any business (or any
         substantial part thereof) used or useful in the same or a similar line
         of business as the Borrower and its Subsidiaries are engaged on the
         Closing Date or other healthcare-related businesses or businesses
         reasonably related thereto.

                  "Eligible Assignee" means (a) a Lender; (b) an Affiliate of a
         Lender; (c) an Approved Fund and (d) any other Person approved by the
         Administrative Agent, the Issuing Lender and the Borrower (such
         approval not to be unreasonably withheld or delayed); provided that (i)
         the Borrower's consent is not required during the existence and
         continuation of a Default or an Event of Default, (ii) approval by the
         Borrower shall be deemed given if no objection is received by the
         assigning Lender and the Administrative Agent from the Borrower within
         five Business Days after notice of such proposed assignment has been
         delivered to the Borrower; (iii) neither the Borrower nor an Affiliate
         of the Borrower shall qualify as an Eligible Assignee; and (iv) no
         competitor of the Borrower shall qualify as an Eligible Assignee.

                  "Guarantor" means each of the Material Domestic Subsidiaries
         of the Borrower, any other Subsidiary of the Borrower that guaranties
         any Pari Passu Debt and each Additional Credit Party, together with
         their successors and assigns.

                  "Leverage Ratio" means, as of the last day of each fiscal
         quarter, the ratio of (a) Funded Debt on such date to (b) EBITDA for
         the twelve month period ending on such date.

                  "Medicaid Regulations" means, collectively, (a) all federal
         statutes (whether set forth in Title XIX of the Social Security Act or
         elsewhere) affecting Medicaid and any statutes succeeding thereto; (b)
         all applicable provisions of all federal rules, regulations, manuals
         and orders and administrative, reimbursement and other guidelines
         having the force of law of all Governmental Authorities promulgated
         pursuant to or in connection with the statutes described in clause (a)
         above; (c) all state statutes and plans for medical assistance enacted
         in connection with the statutes and provisions described in clauses (a)
         and (b) above; and (d) all applicable provisions of all rules,
         regulations, manuals and orders and administrative, reimbursement and
         other guidelines having the force of law of all Governmental
         Authorities promulgated pursuant to or in connection with the statutes
         described in clause (c) above and all state administrative,
         reimbursement and other guidelines of all Governmental Authorities
         having the force of law promulgated pursuant to or in connection with
         the statutes described in clause (b) above, in each case as may be
         amended, supplemented or otherwise modified from time to time.



                                       3







                  "Medicare Provider Agreement" means an agreement entered into
         between CMS or other such entity administering the Medicare program on
         behalf of CMS, and a health care provider or supplier under which the
         health care provider or supplier agrees to provide services for
         Medicare patients in accordance with the terms of the agreement and
         Medicare Regulations.

                  "Medicare Regulations" shall mean, collectively, all federal
         statutes (whether set forth in Title XVIII of the Social Security Act
         or elsewhere) affecting the health insurance program for the aged and
         disabled established by Title XVIII of the Social Security Act and any
         statutes succeeding thereto; together with all applicable provisions of
         all rules, regulations, manuals and orders and administrative,
         reimbursement and other guidelines having the force of law of all
         Governmental Authorities (including, without limitation, the HHS, CMS,
         the OIG, or any person succeeding to the functions of any of the
         foregoing) promulgated pursuant to or in connection with any of the
         foregoing having the force of law, as each may be amended, supplemented
         or otherwise modified from time to time.

                  "OIG" means the Office of Inspector General of HHS and any
         successor thereof.

                  "Permitted Acquisition" means an Acquisition by the Borrower
         or any of its Subsidiaries; provided that (a) substantially all of the
         Property acquired (or the Property of the Person acquired) in such
         Acquisition constitutes Eligible Assets (or goodwill associated
         therewith), (b) in the case of an Acquisition of the Capital Stock of
         another Person, the board of directors (or other comparable governing
         body) of such other Person or its parent shall have duly approved such
         Acquisition, (c) on the date of such Acquisition no Event of Default
         exists, (d) after giving effect to such Acquisition, no Default or
         Event of Default shall exist, (e) if such Acquisition involves the
         formation of a new Subsidiary of the Borrower, such Subsidiary complies
         with Section 7.12 and (f) such Acquisition is undertaken in accordance
         with all laws, rules, regulations, orders, writs, judgments,
         injunctions, decrees and awards to which any party to such Acquisition
         may be subject.

                  "Permitted Investments" means Investments which constitute the
         following: (a) cash or Cash Equivalents, (b) trade accounts receivable
         created, acquired or made in the ordinary course of business, (c)
         inventory, raw materials, general intangibles and other current assets
         acquired in the ordinary course of business, (d) Investments by the
         Borrower or one of its Subsidiaries in each other, (e) Permitted
         Acquisitions, (f) advances to management personnel and employees in the
         ordinary course of business, (g) Investments existing as of the Closing
         Date; provided that any such Investment in excess of $2,000,000 is set
         forth on Schedule 8.6, (h) Investments consisting of non-cash
         consideration received in the form of securities, notes or similar
         obligations in connection with any conveyance, sale, lease, assignment,
         transfer or other disposition of any Property by the Borrower or one of
         its Subsidiaries to any Person, and which are permitted hereunder, and
         (i) any other Investment as long as (i) on the date of such Investment,
         no Event of Default exists and (ii) after giving effect to such
         Investment no Default or Event of Default shall exist.


                                       4








                  "Permitted Liens" means (a) Liens securing Credit Party
         Obligations, if any, (b) Liens for taxes not yet due or Liens for taxes
         being contested in good faith by appropriate proceedings for which
         adequate reserves determined in accordance with GAAP have been
         established (and as to which the Property subject to any such Lien is
         not yet subject to foreclosure, sale, collection, levy or loss on
         account thereof), (c) Liens in respect of Property imposed by law
         arising in the ordinary course of business such as materialmen's,
         mechanics', warehousemen's, carrier's, landlords' and other
         nonconsensual statutory Liens which are not yet due and payable or
         which are being contested in good faith by appropriate proceedings for
         which adequate reserves determined in accordance with GAAP have been
         established (and as to which the Property subject to any such Lien is
         not yet subject to foreclosure, sale or loss on account thereof), (d)
         Liens (other than Liens imposed under ERISA) consisting of pledges or
         deposits made in the ordinary course of business to secure payment of
         worker's compensation insurance, unemployment insurance, pensions or
         social security programs, (e) Liens arising from good faith deposits in
         connection with or to secure performance of tenders, bids, leases,
         government contracts, performance and return-of-money bonds and other
         similar obligations incurred in the ordinary course of business (other
         than obligations in respect of the payment of borrowed money), (f)
         Liens arising from good faith deposits in connection with or to secure
         performance of statutory obligations and surety and appeal bonds, (g)
         easements, rights-of-way, restrictions (including zoning restrictions),
         matters of plat, minor defects or irregularities in title and other
         similar charges or encumbrances not, in any material respect, impairing
         the use of the encumbered Property for its intended purposes, (h)
         judgment Liens that would not constitute an Event of Default, (i) Liens
         in connection with Indebtedness permitted by Sections 8.1(d), (j) Liens
         arising by virtue of any statutory or common law provision relating to
         banker's liens, rights of setoff or similar rights as to deposit
         accounts or other funds maintained with a creditor depository
         institution, (k) Liens existing on the date hereof and identified on
         Schedule 8.2, (l) Liens upon Property acquired (or the Property of a
         Subsidiary that is acquired) after the Effective Date by the Borrower
         or its Subsidiaries, which Liens either (i) existed on such Property
         before the time of such acquisition and was not created in anticipation
         thereof or (ii) were created solely for the purpose of securing
         Indebtedness representing, or incurred to finance or refinance, the
         cost of such Property or improvements thereon; provided, however; that
         (A) no such Lien shall extend to or cover any Property of any Credit
         Party other than the Property so acquired and improvements thereon and
         proceeds thereof, (B) the principal amount of Indebtedness secured by
         any such Lien shall at no time exceed 100% of the fair market value of
         such Property at the time it was acquired or constructed and (C) the
         Indebtedness secured by any such Lien is permitted hereunder; provided
         that (x) no such Lien shall extend to any Property other than the
         Property subject thereto on the closing date of such acquisition and
         (y) the principal amount of the Indebtedness secured by such Liens
         shall not be increased, (m) Liens in connection with Permitted
         Receivables Financing, (n) Liens with respect to lease filings for
         notice purposes only, (o) Liens on purchase money Indebtedness incurred
         by the Borrower in an amount not to exceed, in the aggregate,
         $100,000,000 less Indebtedness incurred by Subsidiaries of the Borrower
         pursuant to Section 8.1(d), (p) Liens on Property of non-wholly owned
         Subsidiaries of the Borrowers incurred to finance working capital and
         (q) renewals and extensions of the foregoing so long as such Lien (i)
         does not



                                       5






         cover any additional Property, (ii) does not secure additional
         Indebtedness and (iii) is not otherwise prohibited by this Credit
         Agreement.

                  "Tender Costs" means the costs incurred by the Borrower in
         connection with any tender for outstanding indebtedness of the
         Borrower, and the termination of the interest rate swap contracts
         related thereto in an aggregate amount not to exceed $35,000,000 during
         the term of this Credit Agreement.

                  (b) New Definitions. The following definitions are added to
         Section 1.1 of the Credit Agreement in the appropriate alphabetical
         order to read as follows:

                  "Approved Fund" means any Fund that is administered or managed
         by (a) a Lender, (b) an Affiliate of a Lender or (c) an entity or an
         Affiliate of an entity that administers or manages a Lender.

                  "CMS" means the Centers for Medicare and Medicaid Services of
         HHS, any successor thereof and any predecessor thereof, including HCFA.

                  "Effective Date" means the Effective Date as defined in the
         2004 Senior Credit Agreement.

                  "Fund" means any Person (other than a natural person) that is
         (or will be) engaged in making, purchasing, holding or otherwise
         investing in commercial loans and similar extensions of credit in the
         ordinary course of its business.

                  "HIPAA" means the Health Insurance Portability and
         Accountability Act of 1996, Pub. L. 104-191, Aug. 21, 1996, 110
         Stat. 1936.

                  "HHS" means the United States Department of Health and Human
         Services and any successor thereof.

                  "Interest Coverage Ratio" means, as of the last day of each
         fiscal quarter, the ratio of (a) EBITDA for the twelve month period
         ending on such date to (b) Cash Interest Expense for the twelve month
         period ending on such date.

                  "Pari Passu Debt" means all unsecured indebtedness of the
         Borrower.

                  (c) References to the 2001 Senior Credit Agreement. The Credit
         Agreement is amended to change all references in the Credit Agreement
         to the "2001 Senior Credit Agreement" to the "2004 Senior Credit
         Agreement."

                  (d) Information Covenants.

                           (1) Section 7.01(a) of the Credit Agreement is
         amended by adding the clause "the earlier of (i)" after the word
         "within" in the first line thereof and adding the



                                       6







         clause "or (ii) ten Business Days after the date the Borrower files
         its Form 10-K with the Securities and Exchange Commission" in the
         second line after the word "Borrower".

                           (2) Section 7.01(b) of the Credit Agreement is
         amended by adding the clause "the earlier of (i)" after the word
         "within" in the first line thereof and adding the clause "or (ii) ten
         Business Days after the date the Borrower files its Form 10-Q with the
         Securities and Exchange Commission" in the second line after the word
         "Borrower".

                           (3) Section  7.01(c) of the Credit Agreement is
         amended by deleting the reference to Section 7.13 therein.

                           (4) A new Section 7.01(i) is added to the Credit
         Agreement to read as follows:

                           (c) Public/Private Information. The Borrower hereby
                  acknowledges that (i) the Administrative Agent will make
                  available to the Lenders materials and/or information provided
                  by or on behalf of the Borrower hereunder (collectively,
                  "Borrower Materials") by posting the Borrower Materials on
                  IntraLinks or another similar electronic system (the
                  "Platform") and (ii) certain of the Lenders may be
                  "public-side" Lenders (i.e., Lenders that do not wish to
                  receive material non-public information with respect to the
                  Borrower or its securities) (each, a "Public Lender"). The
                  Borrower hereby agrees that (A) all Borrower Materials that
                  are to be made available to the Public Lenders shall be
                  clearly and conspicuously marked "PUBLIC" which, at a minimum,
                  shall mean that the word "PUBLIC" shall appear prominently on
                  the first page thereof; (B) by marking Borrower Materials
                  "PUBLIC", the Borrower shall be deemed to have authorized the
                  Administrative Agent and the Lenders to treat such Borrower
                  Materials as either publicly available information or not
                  material information (although it may be sensitive and
                  proprietary) with respect to the Borrower or its securities
                  for purposes of United States federal and state securities
                  laws; (C) all Borrower Materials marked "PUBLIC" are permitted
                  to be made available through a portion of the Platform
                  designated as "Public"; and (D) the Administrative Agent shall
                  be entitled to treat any Borrower Materials that are not
                  marked "PUBLIC" as being suitable only for posting on a
                  portion of the Platform not marked "Public".

                           (5) A new Section 7.01(j) is added to the Credit
         Agreement to read as follows:

                           (d) Electronic Delivery. Documents required to be
                  delivered pursuant to Section 7.1(a) or (b) (to the extent any
                  such documents are included in materials otherwise filed with
                  the Securities and Exchange Commission) may be delivered
                  electronically and if so delivered, shall be deemed to have
                  been delivered on the date (i) on which the Borrower posts
                  such documents, or provides a link thereto on the Borrower's
                  website on the Internet at the website address listed on
                  Schedule 11.1 or (ii) on which such documents are posted on
                  the Borrower's behalf on an Internet or intranet website, if
                  any, to which each Lender and the Administrative Agent have



                                       7







                  access (whether a commercial, third-party website or whether
                  sponsored by the Administrative Agent); provided that: (A) the
                  Borrower shall deliver paper copies of such documents to the
                  Administrative Agent or any Lender that requests the Borrower
                  to deliver such paper copies until a written request to cease
                  delivering paper copies is given by the Administrative Agent
                  or such Lender and (B) the Borrower shall notify (which may be
                  facsimile or electronic mail) the Administrative Agent and
                  each Lender of the posting of any such documents and provide
                  to the Administrative Agent by electronic mail electronic
                  versions (i.e., soft copies) of such documents.
                  Notwithstanding anything contained herein, in every instance
                  the Borrower shall be required to provide paper copies of the
                  compliance certificates required by Section 7.1(c) to the
                  Administrative Agent. Except for such compliance certificates,
                  the Administrative Agent shall have no obligation to request
                  the delivery or to maintain copies of the documents referred
                  to above, and in any event shall have no responsibility to
                  monitor compliance by the Borrower with any such request for
                  delivery, and each Lender shall be solely responsible for
                  requesting delivery to it or maintaining its copies of such
                  documents.

                  (e) Financial Covenants. Section 7.02(b) of the Credit
         Agreement is amended and restated in its entirety to read as follows:

                  (b) Interest Coverage Ratio. The Interest Coverage Ratio, as
         of the last day of each fiscal quarter of the Borrower, shall be
         greater than or equal to 3.5 to 1.0.

                  (f) Compliance with Law. Section 7.05 of the Credit Agreement
         is amended by deleting the words "Titles XVIII and XIX of the Social
         Security Act" and by substituting the word "HIPAA" in replacement
         therefor; by adding the following clause at the end thereof; and making
         the appropriate grammatical and punctuation changes thereto:

                  ;and (iii) no event or related events occur that results in
                  the exclusion of the Borrower or any of its Subsidiaries from
                  participation in any Medical Reimbursement Program and (e)
                  make commercially reasonable efforts to implement policies
                  that are consistent with HIPAA on or before the date that any
                  Credit Party is required to comply therewith.

                  (g) Additional Credit Parties. Section 7.12 of the Credit
         Agreement is amended by changing the reference to "2001 Senior Credit
         Agreement or the Senior Unsecured Notes" to "any Pari Passu Debt".

                  (h) Credit Party Revenues. Section 7.13 of the Credit
         Agreement is deleted in its entirety and Section 7.14 of the Credit
         Agreement is renumbered as Section 7.13.

                  (i) Indebtedness.

                           (1) Section 8.1(d) of the Credit Agreement is amended
         by deleting the number "$50,000,000" and by substituting the number
         "$100,000,000" in replacement therefor.



                                       8






                           (2) Section 8.1(e) of the Credit Agreement is amended
         by deleting the number "$450,000,000" and by substituting the number
         "$600,000,000" in replacement therefor.

                           (3) Section 8.11(h) of the Credit Agreement is
         amended by deleting the term "Closing Date" and substituting the term
         "Effective Date".

                           (4) Schedule 8.1 of the Credit Agreement is amended
         and replaced by the Schedule 8.1 attached hereto.

                  (j) Nature of Business. Section 8.3 of the Credit Agreement
         is amended and restated in its entirety to read as follows:

                  The Borrower will not, nor will it permit its Subsidiaries to,
                  alter the character of its business from that conducted as of
                  the Effective Date or engage in any substantial manner in any
                  business other than (a) the business conducted by the Borrower
                  and its Subsidiaries as of the Effective Date and (b) other
                  healthcare-related businesses and businesses reasonably
                  related thereto.

                  (k) Consolidation and Merger. Section 8.4 of the Credit
         Agreement is amended by deleting the number "$100,000,000" and by
         substituting the number "$750,000,000" in replacement therefor.

                   (l) Transactions with Affiliates. Section 8.7 of the Credit
         Agreement is amended by deleting clause (i) in its entirety; by
         amending and replacing Schedule 8.7 with the Schedule 8.7 attached
         hereto; and by making the appropriate grammatical and punctuation
         changes thereto.

                   (m) Stock Repurchases. Section 8.9 of the Credit Agreement
         is amended and restated in its entirety to read as follows:

                  The Borrower will not, nor will it permit its Subsidiaries to,
                  directly or indirectly, purchase, redeem or otherwise acquire
                  or retire or make any provisions for redemption, acquisition
                  or retirement of any shares of the Capital Stock of the
                  Borrower of any class or any warrants or options to purchase
                  any such shares (collectively, a "Stock Repurchase"); provided
                  that the Borrower or its Subsidiaries may consummate Stock
                  Repurchases as long as on the date of such Stock Repurchase
                  and after giving effect to such Stock Repurchase no Default or
                  Event of Default exists and is continuing.

                  (n) Events of Default.

                           (1) Section 9.1(c)(i) of the Credit Agreement is
         amended by deleting in their entirety the references to Section 7.13
         and Section 7.15 therein.



                                       9





                           (2) Section 9.1(g) of the Credit Agreement is amended
         by deleting the number "$50,000,000" and by substituting the number
         "$100,000,000" in replacement therefor.

                           (3) Section 9.1(h) of the Credit Agreement is amended
         by deleting the number "$50,000,000" and by substituting the number
         "$100,000,000" in replacement therefor.

                           (4) Section 9.1(i) of the Credit Agreement is amended
         by deleting the number "$50,000,000" and by substituting the number
         "$100,000,000" in replacement therefor.

                           (5) Section 9.1(k) of the Credit Agreement is deleted
         in its entirety.

                           (6) Section 9.3 of the Credit Agreement is amended by
         deleting the clause "occurrence and during the continuation of an Event
         of Default" in the first line therof and by substituting the clause
         "the exercise of any remedies by the Administrative Agent or the
         Lenders pursuant to Section 9.2 (or after any Event of Default that
         causes the Commitments to terminate and/or all of the Credit Party
         Obligations to be due hereunder)," in replacement therefor.

                  (o) A new Section 1.5 is added to the Credit Agreement to read
         as follows:

                  0.1 Rounding.

                           Any financial ratios required to be maintained by the
                  Borrower pursuant to this Credit Agreement shall be calculated
                  by dividing the appropriate component by the other component,
                  carrying the result to one place more than the number of
                  places by which such ratio is expressed herein and rounding
                  the result up or down to the nearest number (with a
                  rounding-up if there is no nearest number).

                  (p) A new Section 1.6 is added to the Credit Agreement to read
         as follows:

                  0.2  References to Agreements and Laws.

                           Unless otherwise expressly provided herein, (a)
                  references to organization documents, agreements (including
                  the Credit Documents) and other contractual instruments shall
                  be deemed to include all subsequent amendments, restatements,
                  extensions, supplements and other modifications thereto, but
                  only to the extent that such amendments, restatements,
                  extensions, supplements and other modifications are not
                  prohibited by any Credit Document and (b) references to any
                  law shall include all statutory and regulatory provisions
                  (having the force of law) consolidating, amending, replacing,
                  supplementing or interpreting such law.

                  (q) Section 1.2 of the Credit Agreement is amended and
         restated in its entirety to read as follows:


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         0.3 Other Interpretive Provisions.

                  With reference to this Credit Agreement and each other Credit
                  Document, unless otherwise specified herein or in such other
                  Credit Document:

                  (a) The meanings of defined terms are equally applicable to
                  the singular and plural forms of the defined terms.

                  (b) (i) The words "herein", "hereto", "hereof" and "hereunder"
                  and words of similar import when used in any Credit Document
                  shall refer to such Credit Document as a whole and not to any
                  particular provisions thereof.

                  (ii) Article, Section, Exhibit and Schedule references are to
                  the Credit Document in which such reference appears.

                  (iii) The term "including" is by way of example and not
                  limitation.

                  (iv) the term "documents" includes any and all instruments,
                  documents, agreements, certificates, notices, reports,
                  financial statements and other writings, however evidenced,
                  whether in physical or electronic form.

                  (c) In the computation of periods of time from a specified
                  date to a later specified date, the word "from" means "from
                  and including"; the words "to" and "until" each mean "to but
                  excluding"; and the word "through" means "to and including".

                  (d) Section headings herein and in the other Credit Documents
                  are included for convenience of reference only and shall not
                  affect the interpretation of this Credit Agreement or any
                  other Credit Document.

         2. Effectiveness; Conditions Precedent. This Amendment shall be deemed
to have become effective as of the date above written upon receipt by the
Administrative Agent of copies of this Amendment duly executed by the Credit
Parties and the Lenders.

         3. Ratification of Credit Agreement. The term "Credit Agreement" as
used in each of the Credit Documents shall hereafter mean the Credit Agreement
as amended and modified by this Amendment. Except as herein specifically agreed,
the Credit Agreement, as amended by this Amendment, is hereby ratified and
confirmed and shall remain in full force and effect according to its terms. The
Credit Parties acknowledge and consent to the modifications set forth herein and
agree that this Amendment does not impair, reduce or limit any of their
obligations under the Credit Documents (including, without limitation, the
indemnity obligations set forth therein) and that this Amendment shall
constitute a Credit Document. Notwithstanding anything herein to the contrary
and without limiting the foregoing, each of the Guarantors reaffirms its
guaranty obligations set forth in the Credit Agreement.



                                       11







         4. Authority/Enforceability. 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 Amendment.

                  (b) This Amendment has been duly executed and delivered by
         such Person and constitutes such Person'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 Person of this Amendment.

                  (d) The execution and delivery of this Amendment does not
         violate, contravene or conflict with any Requirement of Law applicable
         to it or any of its Subsidiaries.

         5. No Default. The Credit Parties represent and warrant to the Lenders
that after giving effect to this Amendment (a) the representations and
warranties of the Credit Parties set forth in Section 6 of the Credit Agreement
are true and correct as of the date hereof and (b) no event has occurred and is
continuing which constitutes a Default or an Event of Default.

         6. Release. In consideration of entering into this Amendment, each of
the Credit Parties releases the Agents, the Lenders, and each Agent's and each
Lender's respective Affiliates, Subsidiaries, officers, employees,
representatives, agents, counsel and directors from any and all actions, causes
of action, claims, demands, damages and liabilities of whatever kind or nature,
in law or in equity, now known or unknown, suspected or unsuspected to the
extent that any of the foregoing arises from any action or failure to act with
respect to the Credit Agreement or the other Credit Documents on or prior to the
date hereof.

         7. Counterparts/Telecopy. This 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.
Delivery of executed counterparts of this Amendment by telecopy shall be
effective as an original and shall constitute a representation that an original
shall be delivered promptly upon request.

         8. Entirety. This Amendment and the other Credit Documents embody the
entire agreement between the parties hereto and supersede all prior agreements
and understandings, oral or written, if any, relating to the subject matter
hereof.



                                       12





         9. GOVERNING LAW. THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE
PARTIES HEREUNDER SHALL BE GOVERNED BY AND CONSTRUED AND INTERPRETED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

         10. Venue; Jurisdiction; Waivers. The venue, jurisdiction, waiver of
jury trial and waiver of consequential damages provisions set forth in Sections
11.11 and 11.12 of the Credit Agreement are hereby incorporated by reference,
mutatis mutandis.



                  [remainder of page intentionally left blank]




                                       13










         IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this Amendment to be duly executed and delivered and this Amendment shall be
effective as of the date first above written.


BORROWER:
                                    QUEST DIAGNOSTICS INCORPORATED,
                                    A Delaware corporation

                                    By: /s/ Joseph P. Manory
                                       ---------------------------------
                                    Name:  Joseph P. Manory
                                    Title: Vice President and Treasurer


GUARANTORS:
                                    QUEST DIAGNOSTICS HOLDINGS
                                    INCORPORATED,
                                    a Delaware corporation

                                    QUEST DIAGNOSTICS CLINICAL
                                    LABORATORIES, INC.,
                                    a Delaware corporation

                                    QUEST DIAGNOSTICS INCORPORATED,
                                    a California corporation

                                    QUEST DIAGNOSTICS INCORPORATED,
                                    a Maryland corporation

                                    QUEST DIAGNOSTICS INCORPORATED,
                                    a Michigan corporation

                                    QUEST DIAGNOSTICS OF PENNSYLVANIA, INC.,
                                    a Delaware corporation

                                    METWEST INC.,
                                    a Delaware corporation

                                    NICHOLS INSTITUTE DIAGNOSTICS,
                                    a California corporation

                                    DPD HOLDINGS, INC.,
                                    a Delaware corporation

                                    DIAGNOSTIC REFERENCE SERVICES INC.,
                                    a Maryland corporation



                                       14






                                    AMERICAN MEDICAL LABORATORIES,
                                    INCORPORATED,
                                    a Delaware corporation

                                    AML INC.,
                                    a Delaware corporation

                                    QUEST DIAGNOSTICS INCORPORATED (NV),
                                    a Nevada corporation

                                    QUEST DIAGNOSTICS NICHOLS INSTITUTE, INC.
                                    f/k/a MEDICAL LABORATORIES CORPORATION,
                                    a Virginia corporation

                                    QUEST DIAGNOSTICS LLC,
                                    an Illinois limited liability company

                                    QUEST DIAGNOSTICS LLC,
                                    a Connecticut limited liability company

                                    QUEST DIAGNOSTICS LLC,
                                    a Massachusetts limited liability company

                                    APL PROPERTIES LIMITED LIABILITY COMPANY,
                                    a Nevada limited liability company

                                    UNILAB ACQUISITION CORPORATION,
                                    A Delaware corporation

                                    UNILAB CORPORATION,
                                    A Delaware corporation


                                    By: /s/ Joseph P. Manory
                                       ---------------------------------------
                                    Name:  Joseph P. Manory
                                    Title: Vice President and Treasurer

                                    Of each of the Above Guarantors




                                       15









                                    QUEST DIAGNOSTICS INVESTMENTS
                                    INCORPORATED,
                                    a Delaware corporation

                                    By: /s/ Stephen A. Calamari
                                       ---------------------------------------
                                    Name:  Stephen A. Calamari
                                    Title: Treasurer

                                    QUEST DIAGNOSTICS FINANCE INCORPORATED,
                                    a Delaware corporation

                                    By: /s/ Stephen A. Calamari
                                       ---------------------------------------
                                    Name:  Stephen A. Calamari
                                    Title: Treasurer



                                       16









                                    PATHOLOGY BUILDING PARTNERSHIP,
                                    a Delaware general partnership

                                    By: Quest Diagnostics Incorporated,
                                    a Maryland corporation, its general partner

                                           By: /s/ Joseph P. Manory
                                              ---------------------------------
                                           Name:  Joseph P. Manory
                                           Title: Vice President and Treasurer

                                    By: Diagnostic Reference Services, Inc.,
                                    a Maryland corporation, its general partner

                                           By: /s/ Joseph P. Manory
                                              ---------------------------------
                                           Name:  Joseph P. Manory
                                           Title: Vice President and Treasurer





                                       17






LENDERS:

ADMINISTRATIVE
AGENT AND
INITIAL LENDER:                     SUMITOMO MITSUI BANKING CORPORATION


                                         By: /s/ Robert Riley
                                             ---------------------------------
                                             Name:  Robert Riley
                                             Title: Senior Vice President







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