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.:   0-22758


Forward-Looking Statements:

This communication contains certain forward-looking statements under the Private
Securities Litigation Reform Act of 1995. 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
and a Schedule TO, and Unilab filed a Solicitation/Recommendation Statement on
Schedule 14D-9, 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 filed a Statement on Schedule 13D 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 http://www.sec.gov.

                                   * * * * *

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                                 PRESS RELEASE
--------------------------------------------------------------------------------

Federal Trade Commission Requests More Information From Quest Diagnostics and
Unilab on Pending Acquisition

TETERBORO, N.J., and TARZANA, Calif., May 24 /PRNewswire-FirstCall/ -- Quest
Diagnostics Incorporated (NYSE: DGX - News) and Unilab Corporation (Nasdaq: ULAB
- News) announced that they have received a request for additional information
(commonly referred to as a "second request") from the Federal Trade Commission
(FTC) under the Hart-Scott-Rodino Antitrust Improvements Act (the "HSR Act") in
connection with Quest Diagnostics' pending acquisition of Unilab. The waiting
period under the HSR Act will now expire 30 days after substantial compliance by
both companies with the request for additional information, unless terminated
earlier by the FTC. Quest Diagnostics and Unilab intend to comply with the
request as soon as practicable. Subject to completion of the HSR process and
satisfaction of the other conditions to the cash election exchange offer and the
agreement and plan of merger, the companies anticipate that the acquisition will
close in the third quarter of 2002.

On May 15, 2002, Quest Diagnostics commenced its previously announced cash
election exchange offer for all outstanding Unilab common shares. The exchange
offer is currently scheduled to expire at midnight on Monday, June 17, 2002,
unless extended.

For additional information on the cash election exchange offer, Unilab
shareholders may contact Georgeson Shareholder Communications at 212-440-9800.
In addition, Merrill Lynch is the Dealer Manager for the exchange offer and may
be contacted toll free at 866-276-1462.

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 http://www.questdiagnostics.com.

About Unilab

Unilab Corporation is the largest independent provider of clinical laboratory
testing services in California through its primary testing facilities in Los
Angeles, San Jose and Sacramento and over 400 regional service and testing
facilities located throughout the state. Unilab also operates in the state of
Arizona. Additional information is available on the company's website at
http://www.unilab.com.

Forward-Looking Statements:

This communication contains certain forward-looking statements under the Private
Securities Litigation Reform Act of 1995. 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
and a Schedule TO, and Unilab filed a Solicitation/Recommendation Statement on
Schedule 14D-9, 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 filed a Statement on Schedule 13D 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 http://www.sec.gov.