Pricing Supplement No. 6
Dated July 12, 2001
(to Prospectus dated August 3,
2000 and Prospectus Supplement
dated September 7, 2000)

Merck & Co., Inc.
Medium-Term Notes, Series D
Floating Rate Notes

Principal Amount:   $25,000,000

Trade Date:   July 12, 2001

Settlement Date
(Original Issue Date):

July 18, 2001
Stated Maturity:   July 18, 2041

Base Rate:   LIBOR

Index Maturity:   3 months

Spread:   Minus 45 basis points

Initial Interest Rate:   LIBOR, with an index maturity of 3 months, determined as if the original issue date were an interest reset date, minus the spread

Interest Reset Dates:   The 18th day of July, October, January and April of each year, commencing October 18, 2001

Interest Payment Dates:   The 18th day of July, October, January and April of each year, commencing October 18, 2001

Issue Price:   100.00% of the principal amount

Underwriter's Discount:   1.00% of the principal amount

Net Proceeds to Merck:   99.00% of the principal amount

Calculation Agent:   U.S. Bank Trust National Association

CUSIP:   58933N AS 8

Repayment Dates:
  The notes will be repayable at the option of the holder on notice of not less than 30 days nor more than 60 days on the following optional repayment dates and at the following repayment prices:

  Optional Repayment Date Repayment Price

  July 18, 2011 99.00%

  July 18, 2014 99.25%

  July 18, 2017 99.50%

  July 18, 2020 99.75%

  July 18, 2023 and
July 18 of each
third year thereafter
until maturity

Optional Redemption:   The notes are not subject to optional redemption.

Underwriter:   Merrill Lynch, Pierce, Fenner & Smith

Notes Used as Qualified Replacement Property

         Prospective investors seeking to treat the notes as “qualified replacement property” for purposes of Section 1042 of the Internal Revenue Code of 1986, as amended (the “Code”), should be aware that Section 1042 requires the issuer to meet certain requirements in order for the notes to constitute qualified replacement property. In general, qualified replacement property is a security issued by a domestic “operating corporation” that did not, for the taxable year preceding the taxable year in which such security was purchased, have “passive investment income” in excess of 25 percent of the gross receipts of such corporation for such preceding taxable year (the “Passive Income Test”). A corporation will be considered an “operating corporation” if at the time the securities are purchased or before the end of the replacement period, as defined in Section 1042 of the Code, more than 50 percent of its assets are used in the active conduct of a trade or business. For these purposes, where the issuing corporation is in control of one or more corporations or such issuing corporation is controlled by one or more other corporations, all such corporations are treated as one corporation (the “Affiliated Group”) for the purposes of computing the amount of passive investment income for purposes of Section 1042. Merck believes that it is an “operating corporation” and that less than 25 percent of its Affiliated Group's gross receipts is passive investment income for the taxable year ending December 31, 2000. In making this determination, Merck has made certain assumptions and used procedures which it believes are reasonable. However, the calculation and characterization of certain types of income (as active or passive investment income) in certain of the Affiliated Group's finance and insurance companies is not entirely clear as there are no Treasury regulations or rulings promulgated by the Internal Revenue Service (the “IRS”) that explain the calculation and characterization of such income in circumstances similar to those of Merck's Affiliated Group. Even if such categories of income were treated as passive investment income, Merck believes that the Affiliated Group's passive investment income did not exceed more than 25 percent of the Affiliated Group's gross receipts for the taxable year ending December 31, 2000. No assurance can be given as to whether Merck will continue to meet the Passive Income Test. It is, in addition, possible that the IRS may disagree with the manner in which Merck has calculated the Affiliated Group's gross receipts (incuding the characterization thereof) and passive investment income and the conclusions reached herein.


         Investors that treat the notes as “qualified replacement property” are subject to special rules regarding their basis and holding period in the notes.

         Investors should consult their own tax advisors about the operation of the rules relating to qualified replacement property in their particular circumstances.