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                                                                   Exhibit 99(a)

FOR IMMEDIATE RELEASE

Press Contact: Gregory Reaves                Investor Contact: Laura Jordan
               (908) 423-6022                                  (908) 423-5185



             MERCK REITERATES FOURTH-QUARTER 2000 EARNINGS GUIDANCE


WHITEHOUSE STATION, N.J., Nov. 15, 2000 - Today, Merck Chairman, President and
CEO, Raymond V. Gilmartin, reiterated the Company's comfort with the
fourth-quarter 2000 earnings per share analyst estimates of $0.73 to $0.76. This
guidance was initially reported in the Company's third-quarter earnings release
on October 20, 2000.

         Mr. Gilmartin reiterated this guidance this morning at The Credit
Suisse First Boston Annual Healthcare Conference in Phoenix, Arizona.

         This press release contains "forward-looking statements" as that term
is defined in the Private Securities Litigation Reform Act of 1995. No
forward-looking statement can be guaranteed and actual results may differ
materially from those projected. Additional detailed information concerning a
number of factors that could cause actual results to differ materially is
readily available in Item 1 of the Company's Annual Report on Form 10-K for the
year ended December 31, 1999, in its periodic reports on Form 10-Q and in its
reports on Form 8-K (if any). Copies of these forms are available on request to
Merck's Office of Stockholder Services.

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