SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 11-K
                                  ANNUAL REPORT
                        PURSUANT TO SECTION 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

[X]      ANNUAL REPORT PURSUANT TO SECTION 15 (d) OF THE SECURITIES EXCHANGE ACT
         OF 1934

         For the fiscal year ended December 31, 2002

OR

[  ]     TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE
         ACT OF 1934

         For the transition period from _______to  ____________.

Commission File Number: 1-3305
Employer Identification Number: 66-0288298
Plan Number: 061


              MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
                            (Full title of the plan)

                                MERCK & CO., INC.
          (Name of issuer of the securities held pursuant to the plan)

                                  P.O. Box 100
                    Whitehouse Station, New Jersey 08889-0100
                     (Address of principal executive office)

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
INDEX TO FINANCIAL STATEMENTS AND SUPPLEMENTAL SCHEDULE




                                                                                                 PAGE
                                                                                                 ----

                                                                                             
Report of Independent Accountants                                                                  1

Financial Statements:

    Statements of Net Assets Available for Benefits
      at December 31, 2002 and 2001                                                                2

    Statement of Changes in Net Assets Available for Benefits
      for the year ended December 31, 2002                                                         3

    Notes to Financial Statements                                                                4 - 7

Supplemental Schedule*:

    H - Line 4i - Schedule of Assets (Held at End of Year)                                         8

      Signature                                                                                    9

      Exhibit Index                                                                               10

      Exhibit 23 - Consent of Independent Accountants                                             11

      Exhibit 99.1 - Certification by the Chief Executive Officer of the
        Merck Puerto Rico Employee Savings and Security Plan Pursuant to 18 U.S.C.
        Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002        12

      Exhibit 99.2 - Certification by the Chief Financial Officer of the
        Merck Puerto Rico Employee Savings and Security Plan Pursuant to 18 U.S.C.
        Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002        13




*   Other schedules required by Section 2520.103-10 of the Department of Labor
    Rules and Regulations for Reporting and Disclosure under ERISA have been
    omitted because they are not applicable.

[PRICEWATERHOUSECOOPERS LOGO]

                                                      PRICEWATERHOUSECOOPERS LLP
                                                      254 Munoz Rivera Avenue
                                                      BBV Tower, 9th Floor
                                                      Hato Rey PR 00918
                                                      Telephone (787) 754-9090
                                                      Facsimile (787) 766-1094


                       REPORT OF INDEPENDENT ACCOUNTANTS

To the Participants and Plan Administrator of the
Merck Puerto Rico Employee Savings and Security Plan


In our opinion, the accompanying statements of assets available for benefits and
the related statement of changes in assets available for benefits present
fairly, in all material respects, the assets available for benefits of Merck
Puerto Rico Employee Savings and Security Plan (the "Plan") at December 31, 2002
and 2001, and the changes in assets available for benefits for the year ended
December 31, 2002 in conformity with accounting principles generally accepted in
the United States of America. These financial statements are the responsibility
of the Plan's management; our responsibility is to express an opinion on these
financial statements based on our audits. We conducted our audits of these
statements in accordance with auditing standards generally accepted in the
United States of America, which require that we plan and perform the audit to
obtain reasonable assurance about whether the financial statements are free of
material misstatement. An audit includes examining, on a test basis, evidence
supporting the amounts and disclosures in the financial statements, assessing
the accounting principles used and significant estimates made by management and
evaluating the overall financial statement presentation.  We believe that our
audits provide a reasonable basis for our opinion.

Our audits were conducted for the purpose of forming an opinion on the basic
financial statements taken as a whole. The supplemental Schedule of Assets (Held
at End of Year) is presented for the purpose of additional analysis and is not a
required part of the basic financial statements but is supplementary information
required by the Department of Labor's Rules and Regulations for Reporting and
Disclosure under the Employee Retirement Income Security Act of 1974. This
supplemental schedule is the responsibility of the Plan's management. The
supplemental schedule has been subjected to the auditing procedures applied in
the audits of the basic financial statements and, in our opinion, is fairly
stated in all material respects in relation to the basic financial statements
taken as a whole.

The Schedule of Assets (Held at End of Year) that accompanies the Plan's
financial statements does not disclose the historical cost of certain
nonparticipant directed plan assets held by the Plan's trustee. Disclosure of
this information is required by the Department of Labor's Rules and Regulations
for Reporting and Disclosure under the Employee Retirement Income Securities Act
of 1974.


/s/ PRICEWATERHOUSECOOPERS LLP

May 2, 2003

CERTIFIED PUBLIC ACCOUNTANTS
(OF PUERTO RICO)
License No. 216 Expires Dec. 1, 2004
Stamp 1862757 of the P.R. Society of
Certified Public Accountants has been
affixed to the file copy of the report

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS
DECEMBER 31, 2002 AND 2001






                                             2002              2001
                                          -----------      -----------
                                                     
                 ASSETS

Investments, at market value              $31,257,692      $29,831,972
Participant Loans, at contract value        2,135,301        2,103,597
                                          -----------      -----------

        Total investments                  33,392,993       31,935,569
                                          -----------      -----------

Receivables:
    Employer's contribution                    44,076           40,915
    Participants' contributions               188,942          144,925
    Accrued interest and dividends            167,959          159,598
                                          -----------      -----------

        Total receivables                     400,977          345,438
                                          -----------      -----------

Net assets available for benefits         $33,793,970      $32,281,007
                                          ===========      ===========


   The accompanying notes are an integral part of these financial statements.

                                       2

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS
FOR THE YEAR ENDED DECEMBER 31, 2002





                                                           
Additions to net assets attributed to:
    Investment income:
      Net depreciation in market value of investments         $ (1,555,934)
      Interest and dividends                                       839,322
                                                              ------------
           Net investment loss                                    (716,612)
                                                              ------------
    Contributions to the Plan:
      By participants                                            4,636,974
      By employer                                                1,322,204
                                                              ------------

           Total contributions                                   5,959,178
                                                              ------------

           Total additions                                       5,242,566

Deductions from assets attributed to:
    Benefits paid to participants                               (3,729,603)
                                                              ------------

Net increase in assets available for benefits                    1,512,963

Net assets available for benefits, beginning of the year        32,281,007
                                                              ------------

Net assets available for benefits, end of the year            $ 33,793,970
                                                              ============


   The accompanying notes are an integral part of these financial statements.



                                       3

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2002 AND 2001



1.       DESCRIPTION OF THE PLAN

         The following description of the Merck Puerto Rico Employee Savings and
         Security Plan (the "Plan") provides only general information.
         Participants should refer to the Plan document for a more complete
         description of the Plan's provisions.

         General

         The Plan is a profit sharing plan designed to provide an opportunity
         for employees of Merck Sharp & Dohme Quimica de Puerto Rico, Inc. and
         Merck Sharp & Dohme (I.A.) Corp. (the "Companies") to become
         stockholders of Merck & Co., Inc. ("Merck") and to encourage them to
         save on a regular basis by setting aside part of their earnings.
         Regular full-time and part-time employees of the Companies, as defined
         in the Plan document, who have completed at least one year of
         employment and are not covered by a collective bargaining agreement,
         are eligible to enroll in the Plan.

         The Plan is administered by the Employee Benefits Committee appointed
         by the President of the Companies. All costs of administering the Plan
         are borne by the Companies.

         The Plan is subject to the provisions of the Employee Retirement Income
         Security Act of 1974 (ERISA).

         Contributions

         Participants may contribute from 2% up to 15% of their base pay,
         provided that pre-tax contributions shall not exceed 10% of base
         compensation or $8,000. In addition, the Companies match 50% of pre-tax
         and after-tax employee contributions up to 2.5% of each participant's
         base compensation applicable to the pay period in which the
         contribution is being made. The Companies' matching contributions are
         invested entirely in Merck common stock (non-participant directed) and
         may not be reallocated into any other investment option.

         Participants direct the investment of their contributions into any
         investment option including the Merck Common Stock Fund (participant
         directed). During 2002, the Plan offered 21 investment options: 20
         mutual funds and the Merck Common Stock Fund.

         Participant Accounts

         Each participant account is credited with the participant's
         contribution, the Companies' matching contribution, and allocation of
         Plan earnings. The allocation is based on participants' account
         balances, as defined in the Plan document.

         Vesting

         Participants are immediately vested in their contributions, all
         Companies' matching contributions, plus actual earnings thereon.

         Participant Loans

         Participants may borrow from their account balances with interest
         charged at prime rate plus 1%. Loan terms range from one to five years
         or up to thirty years for the purchase of a primary residence. The
         minimum loan is $500 and the maximum loan is the lesser of $50,000 less
         the highest outstanding loan balance during the one year period prior
         to the new loan application date, or 50% of the participant's account
         balance less any current outstanding loan balance.

                                       4

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2002 AND 2001



         Payment of Benefits

         Participants are entitled to receive automatic, voluntary, in-service
         (which include hardship withdrawals), or mandatory distributions as
         provided in the applicable Plan provisions.

2.       SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

         Basis of Accounting

         The financial statements are prepared on the accrual basis of
         accounting.

         Use of Estimates

         The preparation of financial statements in conformity with accounting
         principles generally accepted in the United States of America requires
         management to make estimates and assumptions that affect the reported
         amounts of assets and liabilities and disclosure of contingent assets
         and liabilities at the date of the financial statements and the
         reported amounts of revenues and expenses during the reporting period.
         Management believes that these estimates are adequate. Actual results
         could differ from those estimates.

         Investment Valuation and Income Recognition

         The investments of the Plan are stated at quoted market prices in an
         active market (except for participant loans which are presented at the
         outstanding balance). Shares of mutual funds are presented at quoted
         market prices which represent the net asset value of the shares held by
         the Plan at the reporting date.

         Purchases and sales of securities are recorded on a trade-date basis.
         Dividend income is recorded on the ex-dividend date. The Plan presents
         in the statement of changes in net assets available for benefits the
         net appreciation (depreciation) in the fair value of its investments
         which consists of the realized gains or losses and the unrealized
         appreciation (depreciation) on them. Interest income on participant
         loans is recorded on accrual basis.

         Contributions

         Employee and Company matching contributions are recorded in the period
         in which the Company makes the payroll deductions from the
         participants' earnings.

         Payment of Benefits

         Benefits are recorded when paid.

         Transfer of Assets to Other Plans

         Company employees or retirees may elect to transfer their savings to
         other plans qualified by the Puerto Rico Department of Treasury or by
         the U.S. Internal Revenue Service (the "IRS").

                                        5

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2002 AND 2001



         Risks and Uncertainties

         The Plan provides for various investment options in investment
         securities. Investment securities, in general, are exposed to various
         risks, such as interest rate, credit and overall market volatility. Due
         to the level of risk associated with certain investment securities, it
         is reasonably possible that changes in the values of investment
         securities will occur in the near term and that such changes could
         materially affect the amounts reported in the statement of net assets
         available for benefits.

         Reclassifications

         Certain reclassifications have been made to prior year financial
         statements to conform with current year presentation.

3.       INVESTMENTS

         The following presents investments that represent 5% or more of the
         Plan's net assets as of year-end.



                                                 2002                      2001
                                                                 
         Shares of Merck Common Stock Fund  $ 27,280,847 *             $ 26,241,792 *

         Participants loans                    2,135,301                  2,103,597



         * Includes non-participant directed portion

         During 2002, the Plan's investments (including gains and losses on
         investments bought and sold, as well as held during the year)
         depreciated in value by $1,555,934 as follows:



                                          2002

                                   
         Mutual Funds                 $  751,050
         Merck Common Stock Fund         804,884
                                      ----------
                                      $1,555,934
                                      ==========


4.       NON-PARTICIPANT DIRECTED INVESTMENTS

         Information about the net assets and the significant components of the
         changes in net assets relating to non-participant directed investments
         is as follows:



                                              2002           2001
                                           ----------      ----------
                                                     
         Assets -
              Merck Common Stock Fund      $8,755,749      $8,399,740
                                           ==========      ==========


                                       6

MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2002 AND 2001





                                                                       YEAR ENDED
                                                                      DECEMBER 31,
                                                                         2002
                                                                     -----------
                                                                  
Changes in net assets:
  Contributions                                                      $ 1,254,938
  Dividends and interest                                                 256,872
  Net depreciation                                                      (262,782)
  Benefits paid to participants                                         (706,564)
  Transfers to participants loan accounts and other plans               (186,455)
                                                                     -----------
                                                                     $   356,009
                                                                     ===========


5.       RELATED PARTY TRANSACTIONS

         Certain Plan investments are shares of mutual funds managed by Fidelity
         Management Trust Company ("Fidelity"). Fidelity is the record keeper as
         defined by the Plan and, therefore, these transactions qualify as
         party-in-interest transactions.

         Merck & Co., Inc. also is a party-in-interest to the Plan under the
         definition provided in Section 3(14) of ERISA. Therefore, Merck Common
         Stock Fund transactions qualify as party-in-interest transactions.

6.       PLAN TERMINATION

         Although they have not expressed any intent to do so, the Companies
         have the right under the Plan to discontinue its contributions at any
         time and to terminate the Plan subject to the provisions of ERISA.

7.       TAX STATUS

         The Plan obtained a tax determination letter from the Puerto Rico
         Department of Treasury dated February 18, 1998 indicating that it had
         been designed in accordance with applicable sections of the Puerto Rico
         Internal Revenue Code of 1994 ("PRIRC") and is, therefore, exempt from
         Puerto Rico income taxes. Therefore, no provision for income taxes has
         been included in the Plan's financial statements.

                                    * * * * *

                                       7

              MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
                    SCHEDULE H, LINE 4I - SCHEDULE OF ASSETS
                              (HELD AT END OF YEAR)



       IDENTITY OF ISSUE, BORROWER,                                                       SHARE                         CURRENT
          LESSOR OR SIMILAR PARTY                  DESCRIPTION OF INVESTMENT             BALANCE           COST          VALUE

                                                                                                         
*   Merck & Co., Inc                    Merck Common Stock                             1,396,153.873       **         $ 27,280,847

*   Fidelity Investments                Fidelity Equity-Income Fund                        3,663.216      ***              145,320

                                        Fidelity Retirement Money Market Fund            732,453.710      ***              732,454

                                        Spartan U.S. Equity Index Fund                     4,251.886      ***              132,446

                                        Spartan Government Income Fund                     2,513.187      ***               28,324

                                        Fidelity Low-Priced Stock Fund                    12,335.918      ***              310,495

                                        Fidelity Dividend Growth Fund                     19,373.789      ***              432,423

    Putnam Investments                  Putnam Vista A Fund                               32,716.789      ***              195,974

                                        Putnam International Voyager  Fund                 1,213.401      ***               16,842

                                        Putnam Global Equity Fund A                          435.243      ***                2,572

    T. Rowe Price                       T. Rowe Price Blue Chip Growth Fund               32,839.173      ***              720,820

    The Vanguard Group                  Vanguard Assets Allocation Fund                   10,228.941      ***              184,837

    The Capital Group Company           American Funds Europacific A                       9,283.349      ***              213,239

    American Century Investment         American Century Emerging Markets
     Services, Inc.                      Investment Fund                                  14,899.927      ***               52,001

    Franklin Templeton                  Franklin Small-Mid Cap Growth Fund A               7,852.960      ***              172,372

    Liberty Wagner Asset                Liberty Acorn Fund - Class Z                       2,261.306      ***               35,050
     Management, L.P.

    Janus                               Janus Enterprises                                    304.708      ***                6,993

                                        Janus Growth & Income                             18,564.916      ***              433,305

    PIMCO                               PIMCO Total Return Fund - Institutional Class      7,806.195      ***               83,292

                                        PIMCO Long-Term Government Fund -
                                        Institutional Class                                6,629.135      ***               73,318

                                        PIMCO Foreign Bond Institution Fund -
                                        Institutional Class                                  450.638      ***                4,768

*   Participants' Loan                  Interest rates ranging from 6.0% to 10.5%
                                        and with maturities through 2012                                  ***            2,135,301

                                         Total                                                                        $ 33,392,993



*   Denotes a party-in-interest to the Plan

**  Historical cost is not available from the Trustee

*** Cost is not required for participant directed investment

                                       8


                                    SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the
undersigned plan administrator has duly caused this annual report to be signed
on behalf of the Merck Puerto Rico Employee Savings and Security Plan by the
undersigned hereunto duly authorized.

                                        Merck & Co., Inc., as plan administrator

                                        By:  /s/ Caroline Dorsa
                                             -----------------------------------
                                             Caroline Dorsa
                                             Vice President & Treasurer


June 27, 2003

                                       9





                                 EXHIBIT INDEX




EXHIBIT
NUMBER         DESCRIPTION                                                 PAGE
-------        -----------                                                 ----
                                                                     
23             Consent of Independent Accountants                          11

99.1           Certification by the Chief Executive Officer of the
               Merck Puerto Rico Employee Savings and Security Plan
               Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant
               to Section 906 of the Sarbanes-Oxley Act of 2002            12

99.2           Certification by the Chief Financial Officer of the
               Merck Puerto Rico Employee Savings and Security Plan
               Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant
               to Section 906 of the Sarbanes-Oxley Act of 2002            13


















                                       10