Exhibit 5.1




                               September 23, 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 $1,000,000 or the equivalent thereof in one or more
foreign currencies: (i) senior debt securities, including the guarantees
endorsed thereon, if any (the "Senior Debt"), and subordinated debt securities,
including the guarantees endorsed thereon, if any (the "Subordinated Debt," and
together with the Senior Debt, the "Debt Securities"); (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 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 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.

          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 each Senior Subsidiary Guarantor, and 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 Company and, if applicable, each Senior Subsidiary
Guarantor, 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 valid and legally binding obligations of the Company and,
if applicable, each Senior Subsidiary Guarantor, enforceable against the Company
and each Senior Subsidiary Guarantor, as the case may be, in accordance with the
terms thereof and will be entitled to the benefits of the Senior Indenture.

          3. The Subordinated Indenture has been duly authorized by the Company
and, when duly authorized by each Subordinated Subsidiary Guarantor, duly
executed and delivered by the Company and each Subordinated Subsidiary Guarantor
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.

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          4. 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, if applicable, each
Subordinated Subsidiary Guarantor, 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 valid and legally
binding obligations of the Company and, if applicable, each Subordinated
Subsidiary Guarantor, enforceable against the Company and each Subordinated
Subsidiary Guarantor, as the case may be, in accordance with the terms thereof
and will be entitled to the benefits of the Subordinated Indenture.

          5. 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.

          6. The Preferred Stock Guarantees have been duly authorized and, when
(i) the final terms thereof have been duly established and approved and (ii) the
Preferred Stock Guarantees have been duly executed by each Preferred Stock
Guarantor and delivered to and paid for by the purchasers thereof, the Preferred
Stock Guarantees will constitute valid and legally binding obligations of each
Preferred Stock Guarantor, enforceable against each Preferred Stock Guarantor,
as the case may be, in accordance with the terms thereof.

          7. 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 (4) and (6) 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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