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                                [FORM OF OPINION]

[To be delivered at Closing pursuant to Section 8.10(c) of the Merger Agreement]


[June] ____ , 2002


Unilab Corporation

18448 Oxnard Street

Tarzana, California  91356

Ladies and Gentlemen:


We have acted as counsel to Unilab Corporation ("Unilab") in connection with the
Offer and the proposed merger (the "Merger") of Unilab with and into Quest
Diagnostics Newco Incorporated ("Merger Sub"), a Delaware corporation and a
direct wholly owned subsidiary of Quest Diagnostics Incorporated, a Delaware
corporation ("Quest"), pursuant to the Agreement and Plan of Merger, dated as of
April 2, 2002 and amended as of May 13, 2002, among Quest, Merger Sub and Unilab
(the "Merger Agreement"). This opinion is being furnished to you pursuant to
Section 8.10(c) of the Merger Agreement. Unless otherwise indicated, each
capitalized term used herein has the meaning ascribed to it in the Merger
Agreement.



In rendering our opinion set forth below, we have examined and, with the consent
of Unilab, Quest and Merger Sub, relied upon the accuracy and completeness
(which we have neither investigated nor verified) of the facts, information,
covenants, representations and warranties contained in originals or copies,
certified or otherwise identified to our satisfaction, of the Merger Agreement,
including the exhibits thereto, the proxy statement/prospectus (the "Proxy
Statement/Prospectus") which is included in the Registration Statement on Form
S-4 of Quest, and such other documents and corporate records as we have deemed
necessary or appropriate as a basis for our opinion set forth below. We have
also relied upon statements and representations made to us by officers and other
representatives of Unilab and Quest (which statements and representations we
have assumed are true without regard to any qualification as to knowledge and
belief), including in their respective letters dated the date hereof (the "Tax
Certificates") and we have assumed that such statements, representations and Tax
Certificates are, and will continue to

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be, complete and accurate.



In rendering our opinion set forth below, we have assumed that (i) the Offer and
the Merger will be consummated in accordance with the terms of the Merger
Agreement and as described in the Proxy Statement/Prospectus and that none of
the terms and conditions contained therein will be or have been waived or
modified in any respect at or prior to the Effective Time and (ii) the Proxy
Statement/Prospectus, the Merger Agreement, the Tax Certificates and such other
documents and records as we have considered reflect all the material facts
relating to the Offer, the Merger, Unilab, Quest and Merger Sub. Our opinion is
conditioned upon, among other things, the initial and continuing accuracy and
completeness of the facts, information, covenants, representations and
warranties made by Unilab and Quest (including, without limitation, those set
forth in the Merger Agreement and the Tax Certificates). Any change or
inaccuracy in the foregoing or the facts referred to, set forth or assumed
herein, in the Proxy Statement/Prospectus, the Merger Agreement or in the Tax
Certificates (giving effect to all events occurring subsequent to the Effective
Time) may affect the conclusions stated herein.



We have also assumed the genuineness of all signatures, the legal capacity of
all natural persons, the authenticity of all documents submitted to us as
originals, the conformity to original documents of all documents submitted to us
as certified or photostatic copies and the authenticity of the originals of such
documents.


In addition, we have considered applicable provisions of the Internal Revenue
Code of 1986, as amended (the "Code"), Treasury Regulations promulgated
thereunder (the "Regulations"), pertinent judicial authorities, rulings of the
Internal Revenue Service (the "IRS") and such other authorities as we have
considered relevant, in each case, in effect on the date hereof. It should be
noted that the Code, the Regulations, judicial decisions, administrative
interpretations and such other authorities are subject to change at any time
and, in some circumstances, with retroactive effect. Additionally, our opinion
is not binding on the IRS or a court and, accordingly, the IRS may assert a
position contrary to our opinion and a court may agree with the IRS's position.
A change in any of the authorities upon which our opinion is based, or any
variation or difference in any fact from those set forth or assumed herein or in
the Proxy Statement/Prospectus, could affect our conclusions stated herein.


Based solely upon and subject to the foregoing and the other limitations,
qualifications, exceptions and assumptions set forth herein, we are of the
opinion that, under current law, the Offer and the Merger will be treated as a
reorganization within the meaning of Section 368(a) of Code for United States
federal income tax purposes.



Except as expressly set forth above, we express no other opinion regarding the
tax consequences of the Offer and/or the Merger. This opinion is for your
benefit and is not to be used, circulated, quoted or otherwise referred to for
any purpose, except that we hereby consent to the reference to this opinion
under the caption "The Offer--Federal Income Tax Consequences" in the Proxy
Statement/Prospectus. The opinion expressed herein is as of the date hereof, and
we disclaim any undertaking to advise you of changes of facts stated or assumed
herein or any subsequent changes in applicable law.

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Very truly yours,


[SKADDEN, ARPS, SLATE, MEAGHER & FLOM LLP]




