<PAGE>   1
      As filed with the Securities and Exchange Commission on July 25, 2001
                                                      Registration No. 333-_____
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                MERCK & CO., INC.
             (Exact Name of Registrant As Specified in Its Charter)
                                  P.O. BOX 100
                                 ONE MERCK DRIVE
                    WHITEHOUSE STATION, NEW JERSEY 08889-0100
                    (Address of Principal Executive Offices)

     NEW JERSEY                                         22-1109110
(State of Incorporation)                    (I.R.S. Employer Identification No.)

                   ROSETTA INPHARMATICS, INC. 1997 STOCK PLAN
                   ROSETTA INPHARMATICS, INC. 2000 STOCK PLAN
          ROSETTA INPHARMATICS, INC. 2000 DIRECTORS' STOCK OPTION PLAN
                            (Full Title of the Plans)

                                CELIA A. COLBERT
              VICE PRESIDENT, SECRETARY & ASSISTANT GENERAL COUNSEL
                                MERCK & CO., INC.
                                  P.O. BOX 100
                                 ONE MERCK DRIVE
                    WHITEHOUSE STATION, NEW JERSEY 08889-0100
                                 (908) 423-1000
            (Name, Address and Telephone Number of Agent for Service)


 If any of the securities being registered on this Form are to be offered on a
  delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
              reinvestment plans, check the following box. [X]

                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
  Title of Securities           Amount to be        Proposed maximum offering        Proposed maximum              Amount of
    to be Registered            Registered (1)         price per share (2)      aggregate offering price (2)      registration fee
<S>                             <C>                 <C>                         <C>                               <C>
      Common Stock
(Par Value $0.01 per share)     750,000 shares             $65.23                     $48,922,500                    $12,230.63
</TABLE>

(1) Represents the maximum number of shares of common stock ("Common Stock"),
    par value $0.01 per share, of Merck & Co., Inc. (the "Company" or
    "registrant") issuable upon exercise of options granted under the Rosetta
    Inpharmatics, Inc. 1997 Stock Plan, the Rosetta Inpharmatics, Inc. 2000
    Stock Plan and the Rosetta Inpharmatics, Inc. 2000 Directors' Stock Option
    Plan (collectively, the "Rosetta Stock Plans") and outstanding immediately
    prior to consummation of the merger (the "Merger") described in the
    Agreement and Plan of Merger (the "Merger Agreement"), dated as of May 10,
    2001, by and among Rosetta Inpharmatics, Inc. ("Rosetta"), the Company and
    Coho Acquisition Corp. (the "Merger Sub").

(2) Based on the price at which the options may be exercised pursuant to Rule
    457(h) of the Securities Act of 1933.
<PAGE>   2
                                EXPLANATORY NOTE

         This Form S-8 relates to 750,000 shares of Common Stock which may be
issued upon the exercise of options granted under the Rosetta Stock Plans.
Pursuant to the Merger Agreement, the following events, among others, have
occurred:

         (a)      Rosetta became a wholly-owned subsidiary of the Company
                  through the merger of Merger Sub with and into Rosetta; and

         (b)      Options to purchase shares of Rosetta common stock granted
                  under the Rosetta Stock Plans outstanding as of the date of
                  consummation of the Merger were converted into options to
                  purchase shares of Common Stock.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

ITEM 1.  PLAN INFORMATION*
ITEM 2.  REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION*

         * Documents containing the information specified in Part I of Form S-8
will be sent or given to each participant in the Rosetta Stock Plans in
accordance with Rule 428(b)(1). In accordance with the Note to Part I of Form
S-8, such documents are not filed with the Securities and Exchange Commission
(the "Commission") either as part of this registration statement (the
"Registration Statement") or as prospectuses or prospectus supplements pursuant
to Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE


         The following documents filed by the registrant with the Commission are
incorporated herein by reference and made a part hereof:

(a)      Annual Report on Form 10-K, filed on March 23, 2001, for the fiscal
         year ended December 31, 2000;

(b)      Quarterly Report on Form 10-Q, filed on May 10, 2001, for the quarter
         ended March 31, 2001;

(c)      Current Report on Form 8-K filed on May 11, 2001;

                                       2
<PAGE>   3
(d)      Form 10-K/A filed on June 20, 2001, amending the registrant's Annual
         Report on Form 10-K for the fiscal year ended December 31, 2000;

(e)      Form 11-K filed on June 22, 2001 for the fiscal year ended December 31,
         2000 for the Merck-Medco Managed Care 401(k) Savings Plan;

(f)      The descriptions of the Common Stock set forth in the registrant's
         Registration Statements pursuant to Section 12 of the Securities
         Exchange Act of 1934 (the "Exchange Act"), and any amendment or report
         filed for the purpose of updating such descriptions.

         All documents subsequently filed by the Company pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment to this Registration Statement which indicates that all
of the shares of Common Stock offered have been sold or which deregisters all of
such shares then remaining unsold, shall be deemed to be incorporated by
reference in this Registration Statement and to be a part hereof from the date
of filing of such documents. An Exhibit Index can be found on page 10 of this
Registration Statement.

         Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this Registration Statement to the extent that a statement
contained herein or in any other subsequently filed document which also is or is
deemed to be incorporated by reference herein modifies or supersedes such
statement. Any such statement so modified or superseded shall not be deemed,
except as so modified or superseded, to constitute a part of this Registration
Statement.

ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         The validity of the Common Stock will be passed upon for the Company by
Celia A. Colbert, Vice President, Secretary & Assistant General Counsel of the
Company.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         The New Jersey Business Corporation Act provides that a New Jersey
corporation has the power to indemnify a director or officer against his or her
expenses and liabilities in connection with any proceeding involving the
director or officer by reason of his or her being or having been such a director
or officer, other than a proceeding by or in the right of the corporation, if
such a director or officer acted in good faith and in a manner he or she
reasonably believed to be in or not opposed to the best interests of the
corporation; and with respect to any criminal proceeding, such director or
officer had no reasonable cause to believe his or her conduct was unlawful.

                                       3
<PAGE>   4
         The indemnification and advancement of expenses shall not exclude any
other rights, including the right to be indemnified against liabilities and
expenses incurred in proceedings by or in the right of the corporation, to which
a director or officer may be entitled under a certificate of incorporation,
bylaw, agreement, vote of stockholders, or otherwise; provided that no
indemnification shall be made to or on behalf of a director or officer if a
judgment or other final adjudication adverse to the director or officer
establishes that his or her acts or omissions (a) were in breach of his or her
duty of loyalty to the corporation or its stockholders, (b) were not in good
faith or involved in a knowing violation of law or (c) resulted in receipt by
the director or officer of an improper personal benefit.

         The Company's Restated Certificate of Incorporation provides that, to
the fullest extent permitted by the laws of the State of New Jersey, directors
and officers of the Company shall not be personally liable to the Company or its
stockholders for damages for breach of any duty owed to the Company or its
stockholders, except that a director or officer shall not be relieved from
liability for any breach of duty based upon an act or omission (a) in breach of
such person's duty of loyalty to the Company or its stockholders, (b) not in
good faith or involving a knowing violation of law or (c) resulting in receipt
by such person of an improper personal benefit.

         The By-Laws of the Company provide that a former, present or future
director, officer or employee of the Company or the legal representative of any
such director, officer or employee shall be indemnified by the Company:

         (a) against reasonable costs, disbursements and counsel fees paid or
incurred where such person has been successful in the defense on the merits or
otherwise of any pending, threatened or completed civil, criminal,
administrative or arbitrative action, suit or proceeding, and any appeal therein
and any inquiry or investigation which could lead to such action, suit or
proceeding or in defense of any claim, issue or matter therein, brought by
reason of such person's being or having been such director, officer or employee,
and

         (b) with respect to the defense of any such action, suit, proceeding,
inquiry or investigation for which indemnification is not made under (a) above,
against reasonable costs, disbursements (which shall include amounts paid in
satisfaction of settlements, judgments, fines and penalties, exclusive, however,
of any amount paid or payable to the Company) and counsel fees if such person
acted in good faith and in a manner such person reasonably believed to be in or
not opposed to the best interests of the Company, and in connection with any
criminal proceedings such person also had no reasonable cause to believe the
conduct was unlawful, with the determination as to whether the applicable
standard of conduct was met to be made by a majority of the members of the Board
of Directors (sitting as a Committee of the Board) who were not parties to such
inquiry, investigation, action, suit or proceeding or by any one or more
disinterested counsel to whom the question may be referred by the Board of
Directors; provided, however, in connection with any proceeding by or in the
right of the Company, no indemnification shall be provided as to any person
adjudged by any court to be liable to the Company except as and to the extent
determined by such court.

         The Company enters into indemnification agreements with its directors
and officers and enters into insurance agreements on its own behalf. The
indemnification agreements provide that


                                       4
<PAGE>   5
the Company agrees to hold harmless and indemnify its directors and officers to
the fullest extent authorized or permitted by the New Jersey Business
Corporation Act, or any other applicable law, or by any amendment thereof or
other statutory provisions authorizing or permitting such indemnification that
is adopted after the date thereof. Without limiting the generality of the
foregoing, the Company agrees to hold harmless and indemnify its directors and
officers to the fullest extent permitted by applicable law against any and all
expenses, judgments, fines and amounts paid in settlement actually and
reasonably incurred by its directors and officers in connection with the defense
of any present or future threatened, pending or completed claim, action, suit or
proceeding by reason of the fact that they were, are, shall be or shall have
been a director or officer of the Company, or are or were serving, shall serve
or shall have served, at the request of the Company, as director or officer of
another corporation, partnership, joint venture, trust, employee benefit plan or
other enterprise.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Not applicable.

ITEM 8.  EXHIBITS
<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------
EXHIBIT
 NUMBER                          DESCRIPTION                                           METHOD OF FILING
-----------------------------------------------------------------------------------------------------------------
<S>                      <C>                                                <C>
  4(a)                   --   Restated Certificate of                       Incorporated by reference to Form
                              Incorporation of the registrant               10-Q Quarterly Report for the period
                              (September 1, 2000)                           ended September 30, 2000

  4(b)                   --   By-Laws of the registrant (as
                              amended effective February 25, 1997)          Incorporated by reference to Form
                                                                            10-Q Quarterly Report for the period
                                                                            ended March 31, 1997

  5                      --   Opinion and Consent of Celia A.               Filed with this Registration Statement
                              Colbert, Vice President, Secretary &
                              Assistant General Counsel of registrant

  23                     --   Consent of Arthur Andersen LLP                Filed with this Registration Statement

  24(a)                  --   Certified Resolution of Board of              Filed with this Registration Statement
                              Directors

  24(b)                  --   Power of Attorney                             Filed with this Registration Statement
-----------------------------------------------------------------------------------------------------------------
</TABLE>


                                       5
<PAGE>   6
ITEM 9.  UNDERTAKINGS

         The undersigned registrant hereby undertakes:

1.       (a) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement to include any
material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change to such
information in the Registration Statement;

         (b) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (c) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

2.       That, for purposes of determining any liability under the Securities
Act of 1933, each filing of the registrant's annual report pursuant to Section
13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

3.       Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the registrant pursuant to the foregoing provisions, or otherwise, the
registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the registrant of expenses incurred
or paid by a director, officer or controlling person of the registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel, the
matter has been settled by controlling precedent, submit to a court of
appropriate jurisdiction the question whether such indemnification by it is
against public policy as expressed in the Act and will be governed by the final
adjudication of such issue.



                                       6
<PAGE>   7
                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the issuer
certifies that it has reasonable grounds to believe that it meets all the
requirements for filing on Form S-8, and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Whitehouse Station and the State of New Jersey on the
25th day of July, 2001.


                                         MERCK & CO., INC.



                                     By:                  *
                                         ---------------------------------------
                                         Raymond V. Gilmartin
                                         Chairman of the Board, President
                                         & Chief Executive Officer



                                     By: /s/ Celia A. Colbert
                                         ---------------------------------------
                                         Celia A. Colbert
                                         Vice President, Secretary &
                                         Assistant General Counsel
                                         (Attorney-in-Fact)







--------------------------------
*        Celia A. Colbert, by signing her name hereto, does hereby sign this
         document pursuant to powers of attorney duly executed by the person
         named, filed with the Securities and Exchange Commission as an exhibit
         to this document, on behalf of such person on the date stated.



                                       7
<PAGE>   8
         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the date indicated.

<TABLE>
<CAPTION>
         SIGNATURES                                                 TITLE                                      DATE
----------------------------------                        ----------------------------                   -------------
<S>                                                       <C>                                            <C>
          *
----------------------------------
Raymond V. Gilmartin                                      Chairman of the Board,                         July 25, 2001
                                                          President & Chief Executive
                                                          Officer; Principal Executive
                                                          Officer; Director

          *
----------------------------------
Judy C. Lewent                                            Executive Vice President &                     July 25, 2001
                                                          Chief Financial Officer;
                                                          Principal Financial Officer


          *
----------------------------------
Richard C. Henriques, Jr.                                 Vice President, Controller;                    July 25, 2001
                                                          Principal Accounting Officer

          *
----------------------------------
Lawrence A. Bossidy                                       Director                                       July 25, 2001

          *
----------------------------------
William G. Bowen, Ph.D.                                   Director                                       July 25, 2001

          *
----------------------------------
Erskine B. Bowles                                         Director                                       July 25, 2001

          *
----------------------------------
Johnnetta B. Cole, Ph.D.                                  Director                                       July 25, 2001

          *
----------------------------------
Niall FitzGerald                                          Director                                       July 25, 2001
</TABLE>



--------------------------------
*        Celia A. Colbert, by signing her name hereto, does hereby sign this
         document pursuant to powers of attorney duly executed by the persons
         named, filed with the Securities and Exchange Commission as an exhibit
         to this document, on behalf of such persons, all in the capacities and
         on the date stated, such persons including a majority of the directors
         of the Company.


                                       8
<PAGE>   9
<TABLE>
<CAPTION>
<S>                                                       <C>                                            <C>
          *
----------------------------------
William B. Harrison, Jr.                                  Director                                       July 25, 2001

          *
----------------------------------
William N. Kelley, M.D.                                   Director                                       July 25, 2001

          *
----------------------------------
Heidi G. Miller                                           Director                                       July 25, 2001

          *
----------------------------------
Edward M. Scolnick, M.D.                                  Director                                       July 25, 2001

          *
----------------------------------
Thomas E. Shenk, Ph.D.                                    Director                                       July 25, 2001

          *
----------------------------------
Anne M. Tatlock                                           Director                                       July 25, 2001

          *
----------------------------------
Samuel O. Thier, M.D.                                     Director                                       July 25, 2001
</TABLE>




--------------------------------
*        Celia A. Colbert, by signing her name hereto, does hereby sign this
         document pursuant to powers of attorney duly executed by the persons
         named, filed with the Securities and Exchange Commission as an exhibit
         to this document, on behalf of such persons, all in the capacities and
         on the date stated, such persons including a majority of the directors
         of the Company.


                                     By: /s/ Celia A. Colbert
                                         ---------------------------------------
                                         Celia A. Colbert
                                         Vice President, Secretary &
                                         Assistant General Counsel
                                         (Attorney-in-Fact)






                                       9
<PAGE>   10
                                  EXHIBIT INDEX


<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------
EXHIBIT
 NUMBER                          DESCRIPTION                                           METHOD OF FILING
-----------------------------------------------------------------------------------------------------------------
<S>                      <C>                                                <C>
  4(a)                   --   Restated Certificate of                       Incorporated by reference to Form
                              Incorporation of the registrant               10-Q Quarterly Report for the period
                              (September 1, 2000)                           ended September 30, 2000

  4(b)                   --   By-Laws of the registrant (as
                              amended effective February 25, 1997)          Incorporated by reference to Form
                                                                            10-Q Quarterly Report for the period
                                                                            ended March 31, 1997

  5                      --   Opinion and Consent of Celia A.               Filed with this Registration Statement
                              Colbert, Vice President, Secretary &
                              Assistant General Counsel of registrant

  23                     --   Consent of Arthur Andersen LLP                Filed with this Registration Statement

  24(a)                  --   Certified Resolution of Board of              Filed with this Registration Statement
                              Directors

  24(b)                  --   Power of Attorney                             Filed with this Registration Statement
-----------------------------------------------------------------------------------------------------------------
</TABLE>




                                       10
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{"company-data": {"conformed-name": "MERCK & CO INC", "cik": "0000064978", "assigned-sic": "2834", "irs-number": "221109110", "state-of-incorporation": "NJ", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-65796", "film-number": "1688781"}, "business-address": {"street1": "ONE MERCK DR", "street2": "P O BOX 100", "city": "WHITEHOUSE STATION", "state": "NJ", "zip": "08889-0100", "phone": "9084234044"}, "mail-address": {"street1": "ONE MERCK DR", "street2": "PO BOX 100 WS3AB-05", "city": "WHITEHOUSE STATION", "state": "NJ", "zip": "08889-0100"}}
1
      As filed with the Securities and Exchange Commission on July 25, 2001
                                                      Registration No. 333-_____
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                MERCK & CO., INC.
             (Exact Name of Registrant As Specified in Its Charter)
                                  P.O. BOX 100
                                 ONE MERCK DRIVE
                    WHITEHOUSE STATION, NEW JERSEY 08889-0100
                    (Address of Principal Executive Offices)

     NEW JERSEY                                         22-1109110
(State of Incorporation)                    (I.R.S. Employer Identification No.)

                   ROSETTA INPHARMATICS, INC. 1997 STOCK PLAN
                   ROSETTA INPHARMATICS, INC. 2000 STOCK PLAN
          ROSETTA INPHARMATICS, INC. 2000 DIRECTORS' STOCK OPTION PLAN
                            (Full Title of the Plans)

                                CELIA A. COLBERT
              VICE PRESIDENT, SECRETARY & ASSISTANT GENERAL COUNSEL
                                MERCK & CO., INC.
                                  P.O. BOX 100
                                 ONE MERCK DRIVE
                    WHITEHOUSE STATION, NEW JERSEY 08889-0100
                                 (908) 423-1000
            (Name, Address and Telephone Number of Agent for Service)

 If any of the securities being registered on this Form are to be offered on a
  delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
              reinvestment plans, check the following box. [X]

                         CALCULATION OF REGISTRATION FEE
Title of Securities           Amount to be        Proposed maximum offering        Proposed maximum              Amount of
    to be Registered            Registered (1)         price per share (2)      aggregate offering price (2)      registration fee
Common Stock
(Par Value $0.01 per share)     750,000 shares             $65.23                     $48,922,500                    $12,230.63
(1) Represents the maximum number of shares of common stock ("Common Stock"),
    par value $0.01 per share, of Merck & Co., Inc. (the "Company" or
    "registrant") issuable upon exercise of options granted under the Rosetta
    Inpharmatics, Inc. 1997 Stock Plan, the Rosetta Inpharmatics, Inc. 2000
    Stock Plan and the Rosetta Inpharmatics, Inc. 2000 Directors' Stock Option
    Plan (collectively, the "Rosetta Stock Plans") and outstanding immediately
    prior to consummation of the merger (the "Merger") described in the
    Agreement and Plan of Merger (the "Merger Agreement"), dated as of May 10,
    2001, by and among Rosetta Inpharmatics, Inc. ("Rosetta"), the Company and
    Coho Acquisition Corp. (the "Merger Sub").

(2) Based on the price at which the options may be exercised pursuant to Rule
    457(h) of the Securities Act of 1933.
2
                                EXPLANATORY NOTE

         This Form S-8 relates to 750,000 shares of Common Stock which may be
issued upon the exercise of options granted under the Rosetta Stock Plans.
Pursuant to the Merger Agreement, the following events, among others, have
occurred:

         (a)      Rosetta became a wholly-owned subsidiary of the Company
                  through the merger of Merger Sub with and into Rosetta; and

         (b)      Options to purchase shares of Rosetta common stock granted
                  under the Rosetta Stock Plans outstanding as of the date of
                  consummation of the Merger were converted into options to
                  purchase shares of Common Stock.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

ITEM 1.  PLAN INFORMATION*
ITEM 2.  REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION*

         * Documents containing the information specified in Part I of Form S-8
will be sent or given to each participant in the Rosetta Stock Plans in
accordance with Rule 428(b)(1). In accordance with the Note to Part I of Form
S-8, such documents are not filed with the Securities and Exchange Commission
(the "Commission") either as part of this registration statement (the
"Registration Statement") or as prospectuses or prospectus supplements pursuant
to Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

         The following documents filed by the registrant with the Commission are
incorporated herein by reference and made a part hereof:

(a)      Annual Report on Form 10-K, filed on March 23, 2001, for the fiscal
         year ended December 31, 2000;

(b)      Quarterly Report on Form 10-Q, filed on May 10, 2001, for the quarter
         ended March 31, 2001;

(c)      Current Report on Form 8-K filed on May 11, 2001;

                                       2
3
(d)      Form 10-K/A filed on June 20, 2001, amending the registrant's Annual
         Report on Form 10-K for the fiscal year ended December 31, 2000;

(e)      Form 11-K filed on June 22, 2001 for the fiscal year ended December 31,
         2000 for the Merck-Medco Managed Care 401(k) Savings Plan;

(f)      The descriptions of the Common Stock set forth in the registrant's
         Registration Statements pursuant to Section 12 of the Securities
         Exchange Act of 1934 (the "Exchange Act"), and any amendment or report
         filed for the purpose of updating such descriptions.

         All documents subsequently filed by the Company pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment to this Registration Statement which indicates that all
of the shares of Common Stock offered have been sold or which deregisters all of
such shares then remaining unsold, shall be deemed to be incorporated by
reference in this Registration Statement and to be a part hereof from the date
of filing of such documents. An Exhibit Index can be found on page 10 of this
Registration Statement.

         Any statement contained in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this Registration Statement to the extent that a statement
contained herein or in any other subsequently filed document which also is or is
deemed to be incorporated by reference herein modifies or supersedes such
statement. Any such statement so modified or superseded shall not be deemed,
except as so modified or superseded, to constitute a part of this Registration
Statement.

ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         The validity of the Common Stock will be passed upon for the Company by
Celia A. Colbert, Vice President, Secretary & Assistant General Counsel of the
Company.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         The New Jersey Business Corporation Act provides that a New Jersey
corporation has the power to indemnify a director or officer against his or her
expenses and liabilities in connection with any proceeding involving the
director or officer by reason of his or her being or having been such a director
or officer, other than a proceeding by or in the right of the corporation, if
such a director or officer acted in good faith and in a manner he or she
reasonably believed to be in or not opposed to the best interests of the
corporation; and with respect to any criminal proceeding, such director or
officer had no reasonable cause to believe his or her conduct was unlawful.

                                       3
4
         The indemnification and advancement of expenses shall not exclude any
other rights, including the right to be indemnified against liabilities and
expenses incurred in proceedings by or in the right of the corporation, to which
a director or officer may be entitled under a certificate of incorporation,
bylaw, agreement, vote of stockholders, or otherwise; provided that no
indemnification shall be made to or on behalf of a director or officer if a
judgment or other final adjudication adverse to the director or officer
establishes that his or her acts or omissions (a) were in breach of his or her
duty of loyalty to the corporation or its stockholders, (b) were not in good
faith or involved in a knowing violation of law or (c) resulted in receipt by
the director or officer of an improper personal benefit.

         The Company's Restated Certificate of Incorporation provides that, to
the fullest extent permitted by the laws of the State of New Jersey, directors
and officers of the Company shall not be personally liable to the Company or its
stockholders for damages for breach of any duty owed to the Company or its
stockholders, except that a director or officer shall not be relieved from
liability for any breach of duty based upon an act or omission (a) in breach of
such person's duty of loyalty to the Company or its stockholders, (b) not in
good faith or involving a knowing violation of law or (c) resulting in receipt
by such person of an improper personal benefit.

         The By-Laws of the Company provide that a former, present or future
director, officer or employee of the Company or the legal representative of any
such director, officer or employee shall be indemnified by the Company:

         (a) against reasonable costs, disbursements and counsel fees paid or
incurred where such person has been successful in the defense on the merits or
otherwise of any pending, threatened or completed civil, criminal,
administrative or arbitrative action, suit or proceeding, and any appeal therein
and any inquiry or investigation which could lead to such action, suit or
proceeding or in defense of any claim, issue or matter therein, brought by
reason of such person's being or having been such director, officer or employee,
and

         (b) with respect to the defense of any such action, suit, proceeding,
inquiry or investigation for which indemnification is not made under (a) above,
against reasonable costs, disbursements (which shall include amounts paid in
satisfaction of settlements, judgments, fines and penalties, exclusive, however,
of any amount paid or payable to the Company) and counsel fees if such person
acted in good faith and in a manner such person reasonably believed to be in or
not opposed to the best interests of the Company, and in connection with any
criminal proceedings such person also had no reasonable cause to believe the
conduct was unlawful, with the determination as to whether the applicable
standard of conduct was met to be made by a majority of the members of the Board
of Directors (sitting as a Committee of the Board) who were not parties to such
inquiry, investigation, action, suit or proceeding or by any one or more
disinterested counsel to whom the question may be referred by the Board of
Directors; provided, however, in connection with any proceeding by or in the
right of the Company, no indemnification shall be provided as to any person
adjudged by any court to be liable to the Company except as and to the extent
determined by such court.

         The Company enters into indemnification agreements with its directors
and officers and enters into insurance agreements on its own behalf. The
indemnification agreements provide that

                                       4
5
the Company agrees to hold harmless and indemnify its directors and officers to
the fullest extent authorized or permitted by the New Jersey Business
Corporation Act, or any other applicable law, or by any amendment thereof or
other statutory provisions authorizing or permitting such indemnification that
is adopted after the date thereof. Without limiting the generality of the
foregoing, the Company agrees to hold harmless and indemnify its directors and
officers to the fullest extent permitted by applicable law against any and all
expenses, judgments, fines and amounts paid in settlement actually and
reasonably incurred by its directors and officers in connection with the defense
of any present or future threatened, pending or completed claim, action, suit or
proceeding by reason of the fact that they were, are, shall be or shall have
been a director or officer of the Company, or are or were serving, shall serve
or shall have served, at the request of the Company, as director or officer of
another corporation, partnership, joint venture, trust, employee benefit plan or
other enterprise.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Not applicable.

ITEM 8.  EXHIBITS
-----------------------------------------------------------------------------------------------------------------
EXHIBIT
 NUMBER                          DESCRIPTION                                           METHOD OF FILING
-----------------------------------------------------------------------------------------------------------------
4(a)                   --   Restated Certificate of                       Incorporated by reference to Form
                              Incorporation of the registrant               10-Q Quarterly Report for the period
                              (September 1, 2000)                           ended September 30, 2000

  4(b)                   --   By-Laws of the registrant (as
                              amended effective February 25, 1997)          Incorporated by reference to Form
                                                                            10-Q Quarterly Report for the period
                                                                            ended March 31, 1997

  5                      --   Opinion and Consent of Celia A.               Filed with this Registration Statement
                              Colbert, Vice President, Secretary &
                              Assistant General Counsel of registrant

  23                     --   Consent of Arthur Andersen LLP                Filed with this Registration Statement

  24(a)                  --   Certified Resolution of Board of              Filed with this Registration Statement
                              Directors

  24(b)                  --   Power of Attorney                             Filed with this Registration Statement
-----------------------------------------------------------------------------------------------------------------
5
6
ITEM 9.  UNDERTAKINGS

         The undersigned registrant hereby undertakes:

1.       (a) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement to include any
material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change to such
information in the Registration Statement;

         (b) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (c) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

2.       That, for purposes of determining any liability under the Securities
Act of 1933, each filing of the registrant's annual report pursuant to Section
13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

3.       Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the registrant pursuant to the foregoing provisions, or otherwise, the
registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the registrant of expenses incurred
or paid by a director, officer or controlling person of the registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel, the
matter has been settled by controlling precedent, submit to a court of
appropriate jurisdiction the question whether such indemnification by it is
against public policy as expressed in the Act and will be governed by the final
adjudication of such issue.

                                       6
7
                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the issuer
certifies that it has reasonable grounds to believe that it meets all the
requirements for filing on Form S-8, and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Whitehouse Station and the State of New Jersey on the
25th day of July, 2001.

                                         MERCK & CO., INC.

                                     By:                  *
                                         ---------------------------------------
                                         Raymond V. Gilmartin
                                         Chairman of the Board, President
                                         & Chief Executive Officer

                                     By: /s/ Celia A. Colbert
                                         ---------------------------------------
                                         Celia A. Colbert
                                         Vice President, Secretary &
                                         Assistant General Counsel
                                         (Attorney-in-Fact)

--------------------------------
*        Celia A. Colbert, by signing her name hereto, does hereby sign this
         document pursuant to powers of attorney duly executed by the person
         named, filed with the Securities and Exchange Commission as an exhibit
         to this document, on behalf of such person on the date stated.

                                       7
8
         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the date indicated.
SIGNATURES                                                 TITLE                                      DATE
----------------------------------                        ----------------------------                   -------------
*
----------------------------------
Raymond V. Gilmartin                                      Chairman of the Board,                         July 25, 2001
                                                          President & Chief Executive
                                                          Officer; Principal Executive
                                                          Officer; Director

          *
----------------------------------
Judy C. Lewent                                            Executive Vice President &                     July 25, 2001
                                                          Chief Financial Officer;
                                                          Principal Financial Officer

          *
----------------------------------
Richard C. Henriques, Jr.                                 Vice President, Controller;                    July 25, 2001
                                                          Principal Accounting Officer

          *
----------------------------------
Lawrence A. Bossidy                                       Director                                       July 25, 2001

          *
----------------------------------
William G. Bowen, Ph.D.                                   Director                                       July 25, 2001

          *
----------------------------------
Erskine B. Bowles                                         Director                                       July 25, 2001

          *
----------------------------------
Johnnetta B. Cole, Ph.D.                                  Director                                       July 25, 2001

          *
----------------------------------
Niall FitzGerald                                          Director                                       July 25, 2001
--------------------------------
*        Celia A. Colbert, by signing her name hereto, does hereby sign this
         document pursuant to powers of attorney duly executed by the persons
         named, filed with the Securities and Exchange Commission as an exhibit
         to this document, on behalf of such persons, all in the capacities and
         on the date stated, such persons including a majority of the directors
         of the Company.

                                       8
9
*
----------------------------------
William B. Harrison, Jr.                                  Director                                       July 25, 2001

          *
----------------------------------
William N. Kelley, M.D.                                   Director                                       July 25, 2001

          *
----------------------------------
Heidi G. Miller                                           Director                                       July 25, 2001

          *
----------------------------------
Edward M. Scolnick, M.D.                                  Director                                       July 25, 2001

          *
----------------------------------
Thomas E. Shenk, Ph.D.                                    Director                                       July 25, 2001

          *
----------------------------------
Anne M. Tatlock                                           Director                                       July 25, 2001

          *
----------------------------------
Samuel O. Thier, M.D.                                     Director                                       July 25, 2001
--------------------------------
*        Celia A. Colbert, by signing her name hereto, does hereby sign this
         document pursuant to powers of attorney duly executed by the persons
         named, filed with the Securities and Exchange Commission as an exhibit
         to this document, on behalf of such persons, all in the capacities and
         on the date stated, such persons including a majority of the directors
         of the Company.

                                     By: /s/ Celia A. Colbert
                                         ---------------------------------------
                                         Celia A. Colbert
                                         Vice President, Secretary &
                                         Assistant General Counsel
                                         (Attorney-in-Fact)

                                       9
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                                  EXHIBIT INDEX
-----------------------------------------------------------------------------------------------------------------
EXHIBIT
 NUMBER                          DESCRIPTION                                           METHOD OF FILING
-----------------------------------------------------------------------------------------------------------------
4(a)                   --   Restated Certificate of                       Incorporated by reference to Form
                              Incorporation of the registrant               10-Q Quarterly Report for the period
                              (September 1, 2000)                           ended September 30, 2000

  4(b)                   --   By-Laws of the registrant (as
                              amended effective February 25, 1997)          Incorporated by reference to Form
                                                                            10-Q Quarterly Report for the period
                                                                            ended March 31, 1997

  5                      --   Opinion and Consent of Celia A.               Filed with this Registration Statement
                              Colbert, Vice President, Secretary &
                              Assistant General Counsel of registrant

  23                     --   Consent of Arthur Andersen LLP                Filed with this Registration Statement

  24(a)                  --   Certified Resolution of Board of              Filed with this Registration Statement
                              Directors

  24(b)                  --   Power of Attorney                             Filed with this Registration Statement
-----------------------------------------------------------------------------------------------------------------
10