Exhibit 15

August 3, 2004

To the Shareholders and Board of Directors of
Schering-Plough Corporation:

We have made a review, in accordance with the standards of the Public Company
Accounting Oversight Board (United States), of the unaudited interim financial
information of Schering-Plough Corporation and subsidiaries for the periods
ended June 30, 2004 and 2003, as indicated in our report dated July 30, 2004;
because we did not perform an audit, we expressed no opinion on that
information.

We are aware that our report referred to above, which is included in your
Quarterly Report on Form 10-Q for the quarter ended June 30, 2004, is
incorporated by reference in Registration Statements No. 2-83963, No. 33-19013,
No. 33-50606, No. 333-30331, No. 333-87077, No. 333-91440, No. 333-104714, No.
333-105567, No. 333-105568 and No. 333-112421 on Form S-8, Post Effective
Amendment No. 1 to Registration Statement No. 2-84723 on Form S-8, Post
Effective Amendment No. 1 to Registration Statement No. 333-105567 on Form S-8,
Post Effective Amendment No. 1 to Registration Statement No. 2-80012 on Form
S-3, Post Effective Amendment No. 1 to Registration Statement No. 2-77740 on
Form S-3, Post Effective Amendment No. 1 to Registration Statement No.
333-102970 on Form S-3 and Registration Statements No. 333-12909, No. 333-853,
No. 333-30355, No. 333-102970, No. 333-110690 and No. 333-113222 on Form S-3.

We also are aware that the aforementioned report, pursuant to Rule 436(c) under
the Securities Act of 1933, is not considered a part of the Registration
Statements prepared or certified by an accountant or a report prepared or
certified by an accountant within the meaning of Sections 7 and 11 of that Act.

/s/ Deloitte & Touche LLP

Parsippany, New Jersey