November 26, 2003

The Board of Directors
Quest Diagnostics Incorporated
One Malcolm Avenue
Teterboro, New Jersey 07608

                         Quest Diagnostics Incorporated

Ladies and Gentlemen:

          We have acted as counsel for Quest Diagnostics Incorporated (the
"Company") in connection with the preparation of a registration statement on
Form S-3 (the "Registration Statement") filed with the Securities and Exchange
Commission (the "Commission") relating to the offering from time to time,
pursuant to Rule 415 of the General Rules and Regulations of the Commission
promulgated under the Securities Act of 1933, as amended (the "Securities Act"),
by the Company of the following securities of the Company with an aggregate
offering price of up to $650,000,000 or the equivalent thereof in one or more
foreign currencies: (i) senior debt securities (the "Senior Debt"), including
the guarantees endorsed thereon, if any (the "Senior Subsidiary Guarantees"),
and subordinated debt securities (the "Subordinated Debt," and together with the
Senior Debt, the "Debt Securities"), including the guarantees endorsed thereon,
if any (the "Subordinated Subsidiary Guarantees"); (ii) preferred stock (the
"Preferred Stock") and the guarantees, if any, thereof by subsidiaries of the
Company (the "Preferred Stock Guarantees"); and (iii) common stock (the "Common
Stock"), including common stock that may be issued upon conversion of the Debt
Securities or Preferred Stock. The Debt Securities, the Preferred Stock and the
Common Stock are collectively referred to as the "Securities." The offering of
the Securities will be as set forth in the prospectus contained in the
Registration Statement (the "Prospectus"), as supplemented by one or more
supplements to the Prospectus (each supplement, a "Prospectus Supplement").

          The Senior Debt and the Senior Subsidiary Guarantees will be issued in
one or more series pursuant to an indenture dated as of June 27, 2001, as
supplemented by the First Supplemental Indenture dated as of June 27, 2001, as
further supplemented by the Second Supplemental Indenture dated as of November
26, 2001, as further supplemented by the Third Supplemental Indenture dated as
of April 4, 2002 and as further supplemented by the Fourth Supplemental
Indenture dated as of March 19, 2003 (collectively, the "Senior Indenture"), in
each case, among the Company, the subsidiaries of the Company indicated on the
signature pages thereto, as guarantors (the "Senior Subsidiary Guarantors"), and
The Bank of New York, as trustee (the "Senior Trustee"). The Subordinated Debt
and the Subordinated Subsidiary







Guarantees will be issued in one or more series pursuant to a subordinated
indenture (the "Subordinated Indenture") to be entered into among the Company,
the subsidiaries of the Company indicated on the signature pages thereto, as
guarantors (the "Subordinated Subsidiary Guarantors"), and The Bank of New York,
as trustee (the "Subordinated Trustee"). The subsidiaries of the Company, if
any, which are guarantors of the Preferred Stock are referred to herein as the
"Preferred Stock Guarantors." The Senior Subsidiary Guarantors, the Subordinated
Subsidiary Guarantors and the Preferred Stock Guarantors are referred to
collectively as the "Subsidiary Guarantors."

          In our capacity as counsel to the Company, we have examined (i) the
Registration Statement, (ii) the Senior Indenture filed as an exhibit to the
Registration Statement, (iii) the form of Subordinated Indenture filed as an
exhibit to the Registration Statement, and (iv) the originals, or copies
identified to our satisfaction, of such corporate records of the Company and the
Subsidiary Guarantors, certificates of public officials, officers of the Company
and other persons, and such other documents, agreements and instruments as we
have deemed necessary as a basis for the opinions hereinafter expressed. In our
examination, we have assumed the legal capacity of all natural persons, the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals, the conformity with the originals of all documents submitted to us
as copies.

          In rendering our opinion, we have assumed (i) that each of the
Subsidiary Guarantors is duly organized and validly existing in good standing in
its jurisdiction of incorporation or formation and has all requisite corporate
power and authority to execute, deliver and perform its obligations under the
Senior Indenture and the Senior Subsidiary Guarantees, the Subordinated
Indenture and the Subordinated Subsidiary Guarantees, or the Preferred Stock
Guarantees, as the case may be, (ii) the due authorization by all necessary
corporate action on the part of each of the Subsidiary Guarantors of the
execution, delivery and performance of the Senior Indenture and the Senior
Subsidiary Guarantees, the Subordinated Indenture and the Subordinated
Subsidiary Guarantees, or the Preferred Stock Guarantees, as the case may be,
and (iii) the due execution and delivery by each of the Subsidiary Guarantors of
the Senior Indenture and the Senior Subsidiary Guarantees, the Subordinated
Indenture and the Subordinated Subsidiary Guarantees, or the Preferred Stock
Guarantees, as the case may be.

          Our opinions set forth below are limited to the laws of the State of
New York, the General Corporation Law of the State of Delaware and the federal
laws of the United States and we do not express any opinion herein concerning
any other laws.

          Based on the foregoing, we are of the opinion that:

          1. The Senior Indenture has been duly authorized, executed and
delivered by the Company, and assuming due authorization, execution and delivery
by the Senior Trustee, the Senior Indenture constitutes a valid and legally
binding obligation of the Company and each Senior Subsidiary Guarantor,
enforceable against the Company and each Senior Subsidiary Guarantor in
accordance with its terms.

          2. The Senior Debt has been duly authorized and, when (i) the final
terms thereof have been duly established and approved and (ii) the Senior Debt
has been duly executed by the


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Company and authenticated by the Senior Trustee in accordance with the Senior
Indenture and delivered to and paid for by the purchasers thereof, the Senior
Debt will constitute a valid and legally binding obligation of the Company,
enforceable against the Company in accordance with the terms thereof and will be
entitled to the benefits of the Senior Indenture.

          3. When (i) the final terms of the Senior Subsidiary Guarantees have
been duly established and approved and (ii) the Senior Subsidiary Guarantees
have been duly executed by the Senior Subsidiary Guarantors and when the Senior
Debt has been duly executed by the Company and authenticated by the Senior
Trustee in accordance with the provisions of the Senior Indenture and delivered
to and paid for by the purchasers thereof, the Senior Subsidiary Guarantees will
constitute a valid and binding obligation of each Senior Subsidiary Guarantor
which issued such Senior Subsidiary Guarantees, enforceable against such Senior
Subsidiary Guarantor in accordance with their terms thereof.

          4. The Subordinated Indenture has been duly authorized by the Company
and, when duly executed and delivered by the Company and duly authorized,
executed and delivered by the Subordinated Trustee, the Subordinated Indenture
will constitute a valid and legally binding obligation of the Company and each
Subordinated Subsidiary Guarantor, enforceable against the Company and each
Subordinated Subsidiary Guarantor in accordance with its terms.

          5. The Subordinated Debt has been duly authorized and, when (i) the
final terms thereof have been duly established and approved and (ii) the
Subordinated Debt has been duly executed by the Company and authenticated by the
Subordinated Trustee in accordance with the Subordinated Indenture and delivered
to and paid for by the purchasers thereof, the Subordinated Debt will constitute
a valid and legally binding obligation of the Company, enforceable against the
Company in accordance with the terms thereof and will be entitled to the
benefits of the Subordinated Indenture.

          6. When (i) the final terms of the Subordinated Subsidiary Guarantees
have been duly established and approved and (ii) the Subordinated Subsidiary
Guarantees have been duly executed by the Subordinated Subsidiary Guarantors and
when the Subordinated Debt has been duly executed by the Company and
authenticated by the Subordinated Trustee in accordance with the provisions of
the Subordinated Indenture and delivered to and paid for by the purchasers
thereof, the Subordinated Subsidiary Guarantees will constitute a valid and
binding obligation of each Subordinated Subsidiary Guarantor which issued such
Subordinated Subsidiary Guarantees, enforceable against such Subordinated
Subsidiary Guarantor in accordance with their terms thereof.

          7. When (i) all corporate action necessary for issuance of the
Preferred Stock has been taken, including the adoption of a Certificate of
Designations relating thereto, (ii) the final terms of the Preferred Stock have
been duly established and approved and (iii) the shares of Preferred Stock have
been duly issued and delivered to and paid for by the purchasers thereof, the
Preferred Stock will be validly issued, fully paid and non-assessable.

          8. When (i) the final terms of the Preferred Stock Guarantees have
been duly established and approved and (ii) the Preferred Stock Guarantees have
been duly executed by each Preferred Stock Guarantor and when the shares
of Preferred Stock have been duly issued and delivered to and paid for by the
purchasers thereof, the Preferred Stock Guarantees will constitute valid and
legally binding obligations of each Preferred


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Stock Guarantor, enforceable against each Preferred Stock Guarantor, as the case
may be, in accordance with the terms thereof.

          9. The Company has authority pursuant to its Certificate of
Incorporation to issue up to 300,000,000 shares of Common Stock. When (i) all
corporate action necessary for the issuance of the Common Stock has been taken
and (ii) such shares of Common Stock have been duly issued and delivered to and
paid for by the purchasers thereof, the Common Stock will be validly issued,
fully paid and non-assessable.

          The opinions set forth in paragraphs (1) through (6) and (8) above are
subject, as to enforcement, to (i) bankruptcy, insolvency, reorganization,
moratorium or other similar laws relating to or affecting creditors' rights
generally (including, without limitation, all laws relating to fraudulent
transfers), (ii) general principles of equity (regardless of whether enforcement
is considered in a proceeding in equity or at law) and (iii) provisions of law
that require that a judgment for money damages rendered by a court in the United
States be expressed only in United States dollars.

          We hereby consent to the use of this opinion as an exhibit to the
Registration Statement and to the use of our name under the heading "Validity of
the Securities" in the Prospectus.

                                            Very truly yours,

                                            /S/ SHEARMAN & STERLING LLP


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