Medicines (MDCO) 10-Q 2006 Q2 Quarterly report

EXHIBIT 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report on Form 10-Q of The Medicines Company (the “Company”) for the period ended June 30, 2006 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Clive A. Meanwell, Chairman and Chief Executive Officer of the Company, hereby certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1)The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

		By:	/s/ Clive A. Meanwell
Dated:	August 8, 2006	Clive A. Meanwell
		Chairman and Chief Executive Officer