Filed by:     Quest
                                                        Diagnostics Incorporated


                       This communication is filed pursuant to Rules 165 and 425
                       promulgated under the Securities Act of 1933, as amended.

                                             Subject Company: Unilab Corporation
                                         Commission File No.:    00-11839



FORWARD-LOOKING STATEMENTS:
This communication contains certain forward-looking statements. These
forward-looking statements, which may include, but are not limited to,
statements concerning the financial condition, results of operations and
businesses of Quest Diagnostics and Unilab and the benefits expected to result
from the contemplated transaction, are based on management's current
expectations and estimates and involve risks and uncertainties that could cause
actual results or outcomes to differ materially from those contemplated by the
forward-looking statements.

Factors that could cause or contribute to such differences may include, but are
not limited to, the risk that the conditions relating to the required minimum
tender of Unilab shares or regulatory clearance might not be satisfied in a
timely manner or at all, risks relating to the integration of the technologies
and businesses of Quest Diagnostics and Unilab, unanticipated expenditures,
changing relationships with customers, suppliers and strategic partners,
conditions of the economy and other factors described in the most recent reports
on Form 10-Q, most recent reports on Form 10-K, and other periodic reports filed
by Quest Diagnostics and Unilab with the Securities and Exchange Commission.

ADDITIONAL INFORMATION:
On May 15, 2002, Quest Diagnostics filed a Registration Statement on Form S-4,
as amended, and a Schedule TO, as amended, and Unilab filed a
Solicitation/Recommendation Statement on Schedule 14D-9, as amended, with the
Securities and Exchange Commission in connection with the transaction. A
Prospectus, which is part of the Registration Statement on Form S-4, the
Solicitation/Recommendation Statement on Schedule 14D-9, and related exchange
offer materials, including a letter of election and transmittal, have been
mailed to stockholders of Unilab. In addition, Quest Diagnostics has previously
filed a Statement on Schedule 13D, as amended, relating to its agreement with
Kelso Investment Associates VI, L.P. and KEP VI, LLC. Investors and stockholders
of Unilab are urged to read all of these documents carefully. These documents
contain important information about the transaction and should be read before
any decision is made with respect to the exchange offer. Investors and
stockholders are able to obtain free copies of these documents through the
website maintained by the Securities and Exchange Commission at www.sec.gov.
Free copies of these documents may also be obtained from Quest Diagnostics by
directing a request to Quest Diagnostics Incorporated at One Malcolm Avenue,
Teterboro, New Jersey, 07608, or from Unilab by directing a request to Unilab
Corporation at 18448 Oxnard Street, Tarzana, California, 91356.




In addition to the Registration Statement on Form S-4, Schedule TO, Prospectus,
Solicitation/Recommendation Statement on Schedule 14D-9 and related exchange
offer materials, both Quest Diagnostics and Unilab file annual, quarterly and
special reports, proxy statements and other information with the Securities and
Exchange Commission. You may read and copy any reports, Statements or other
information filed by Quest Diagnostics or Unilab at the SEC public reference
room at 450 Fifth Street, N.W., Washington, D.C., 20549, or at any of the
Securities and Exchange Commission's other public reference rooms in New York,
New York and Chicago, Illinois. Please call the Securities and Exchange
Commission at 800-SEC-0330 for further information on the public reference
rooms. Quest Diagnostics' and Unilab's filings with the Securities and Exchange
Commission are also available to the public from commercial document-retrieval
services and at the website maintained by the Securities and Exchange Commission
at www.sec.gov.

                                      # # #


                  Quest Diagnostics Incorporated
                  One Malcolm Avenue
                  Teterboro, New Jersey 07608

[LOGO]                                             News From Quest Diagnostics
                                                   ---------------------------
Contacts:

Laure Park (Investors): 201-393-5030
Gary Samuels (Media): 201-393-5700


                                                       FOR IMMEDIATE RELEASE
                                                       ---------------------

   QUEST DIAGNOSTICS TO SELL CERTAIN ASSETS IN NORTHERN CALIFORNIA TO LABCORP
        - Quest Diagnostics Extends Exchange Offer for Shares of Unilab -

TETERBORO, N.J., February 4, 2003 -- Quest Diagnostics Incorporated (NYSE: DGX)
announced that it had executed an agreement, subject to approval by the Federal
Trade Commission, to sell certain assets in Northern California to Laboratory
Corporation of America (NYSE: LH) (LabCorp(R)) for $4.5 million cash. In
addition, Quest Diagnostics announced that it has extended the expiration date
for its previously announced cash election exchange offer for all outstanding
shares of Unilab Corporation common stock. The offer was extended by five
business days and will now expire at 12:00 midnight, New York City time, on
Monday, February 10, 2003, unless extended.

The assets to be sold to LabCorp include the assignment of four capitated
contracts with independent physician associations (IPAs), as well as the leases
for 46 patient service centers, five of which also serve as rapid response
laboratories located throughout Northern California. Approximately $27 million
in annual revenues are generated by capitated fees under the IPA contracts and
associated fee-for-service testing for physicians whose patients use these
patient



service centers, as well as from specimens received directly from the IPA
physicians. The IPAs have already consented to the assignment of the contracts.

The asset sale to LabCorp is subject to approval by the Federal Trade Commission
and is contingent on and will close after the completion of the Quest
Diagnostics/Unilab transaction. As previously announced, the FTC has not yet
completed its review of the Quest Diagnostics/Unilab transaction. Quest
Diagnostics and Unilab hope to receive FTC approval within the five-business-day
extension period, and, accordingly, to complete the Exchange Offer on February
11, 2003. However, there can be no assurance as to whether or when the necessary
FTC approval will be obtained.

As of 12:00 midnight, New York City time, on February 3, 2003, more than 32
million shares of Unilab Corporation common stock had been tendered,
representing approximately 97% of the outstanding Unilab Corporation common
stock.

About Quest Diagnostics
Quest Diagnostics Incorporated is the nation's leading provider of diagnostic
testing, information and services, providing insights that enable physicians,
hospitals, managed care organizations and other healthcare professionals to make
decisions to improve health. The company offers the broadest access to
diagnostic laboratory services through its national network of laboratories and
patient service centers. Quest Diagnostics is the leading provider of esoteric
testing, including gene-based medical testing, and empowers healthcare
organizations and clinicians with state-of-the-art connectivity solutions that
improve practice management. Additional company information can be found on the
Internet at: www.questdiagnostics.com.

FORWARD-LOOKING STATEMENTS:
This communication contains certain forward-looking statements. These
forward-looking statements, which may include, but are not limited to,
statements concerning the financial condition, results of operations and
businesses of Quest Diagnostics and Unilab and the benefits expected to result
from the contemplated transaction, are based on management's current
expectations and estimates and involve risks and uncertainties that could cause
actual results or outcomes to differ materially from those contemplated by the
forward-looking statements.

Factors that could cause or contribute to such differences may include, but are
not limited to, the risk that the conditions relating to the required minimum
tender of Unilab shares or regulatory clearance might not be satisfied in a
timely manner or at all, risks relating to the integration of the technologies
and businesses of Quest Diagnostics and Unilab, unanticipated expenditures,
changing relationships with customers, suppliers and strategic partners,
conditions of the economy and other factors described in the most recent reports
on Form 10-Q, most recent reports on Form 10-K, and other periodic reports filed
by Quest Diagnostics and Unilab with the Securities and Exchange Commission.

ADDITIONAL INFORMATION:

On May 15, 2002, Quest Diagnostics filed a Registration Statement on Form S-4,
as amended, and a Schedule TO, as amended, and Unilab filed a
Solicitation/Recommendation Statement on Schedule 14D-9, as amended, with the
Securities and Exchange Commission in connection with the transaction. A
Prospectus, which is part of the Registration Statement on Form S-4, the
Solicitation/Recommendation Statement on Schedule 14D-9, and related exchange
offer materials, including a letter of election and transmittal, has been mailed
to stockholders of Unilab. In addition, Quest Diagnostics has previously filed a
Statement on Schedule 13D, as amended, relating to its agreement with Kelso
Investment Associates VI, L.P. and KEP VI, LLC. Investors and stockholders of
Unilab are urged to read all of these documents carefully. These




documents contain important information about the transaction and should be read
before any decision is made with respect to the exchange offer. Investors and
stockholders are able to obtain free copies of these documents through the
website maintained by the Securities and Exchange Commission at www.sec.gov.
Free copies of these documents may also be obtained from Quest Diagnostics by
directing a request to Quest Diagnostics Incorporated at One Malcolm Avenue,
Teterboro, New Jersey, 07608, or from Unilab by directing a request to Unilab
Corporation at 18448 Oxnard Street, Tarzana, California, 91356.

In addition to the Registration Statement on Form S-4, Schedule TO, Prospectus,
Solicitation/Recommendation Statement on Schedule 14D-9 and related exchange
offer materials, both Quest Diagnostics and Unilab file annual, quarterly and
special reports, proxy statements and other information with the Securities and
Exchange Commission. You may read and copy any reports, Statements or other
information filed by Quest Diagnostics or Unilab at the SEC public reference
room at 450 Fifth Street, N.W., Washington, D.C., 20549, or at any of the
Securities and Exchange Commission's other public reference rooms in New York,
New York and Chicago, Illinois. Please call the Securities and Exchange
Commission at 800-SEC-0330 for further information on the public reference
rooms. Quest Diagnostics' and Unilab's filings with the Securities and Exchange
Commission are also available to the public from commercial document-retrieval
services and at the website maintained by the Securities and Exchange Commission
at www.sec.gov.

                                      # # #