Exhibit 32.1

CERTIFICATION

I, Fred Hassan, Chairman of the Board, Chief Executive Officer and President of
Schering-Plough Corporation, certify, pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, that:

(1)   the Quarterly Report on Form 10-Q for the quarterly period ended June 30,
      2004 (the "Periodic Report") which this statement accompanies fully
      complies with the requirements of Section 13(a) of the Securities Exchange
      Act of 1934 (15 U.S.C. 78m); and

(2)   information contained in the Periodic Report fairly presents, in all
      material respects, the financial condition and results of operations of
      Schering-Plough Corporation.

Dated: August 3, 2004

/s/ Fred Hassan
--------------------------
Fred Hassan
Chairman of the Board,
Chief Executive Officer
and President