Exhibit 99.1

SCHERING-PLOUGH ENTERS INTO STRATEGIC ALLIANCE WITH BAYER

KENILWORTH, N.J., Sept. 13, 2004 -- Schering-Plough Corporation (NYSE: SGP)
today announced that it has entered into a strategic agreement with Bayer
designed to maximize the companies' pharmaceutical resources while maintaining
each company's own strategic interests. The agreement is expected to be
effective Oct. 1, 2004.

     In the United States and Puerto Rico, Schering-Plough has acquired
exclusive rights to market, sell and distribute Bayer's primary care products
AVELOX (moxifloxacin HCl) and CIPRO (ciprofloxacin HCl) in the antibiotics
category and will undertake on behalf of Bayer the U.S. commercialization
activities for the erectile dysfunction medicine LEVITRA (vardenafil HCl) under
Bayer's co-promotion agreement with GlaxoSmithKline PLC. The addition of these
products is expected to strengthen Schering-Plough's primary care presence in
the United States, with the goal of more effectively realizing the potential of
the Schering-Plough and Bayer primary care product portfolios. In the Japanese
market, Bayer will co-market Schering-Plough's novel cholesterol absorption
inhibitor ZETIA(R) (ezetimibe), currently under regulatory review in Japan,
leveraging Bayer's established expertise and relationships with cardiovascular
specialists to enhance the local launch of the product. Additionally, under the
terms of the agreement, Bayer will support the promotion of certain
Schering-Plough oncology products in the United States and key European markets
for a defined period of time.

     "This strategic agreement represents a further step in our Action Agenda to
build the New Schering-Plough," said Fred Hassan, Schering-Plough chairman and
chief executive officer. "The collaboration will enhance our primary care
product line and complement our respiratory franchise. We anticipate that it
will also strengthen our presence in Japan through the co-marketing of ZETIA
with Bayer in this key cardiovascular market, pending approval by Japanese
authorities."

     Under the agreement, there will be a business integration and transition
period during the remainder of 2004. For Schering-Plough, the transaction is
expected to be mildly dilutive in 2004 in terms of its impact on earnings per
share. Thereafter, the transaction is expected to be mildly accretive. Products
in development at both companies are not covered under the agreement. Bayer's
drug products will remain the property and legal responsibility of Bayer and
continue to be sold under the Bayer brand names.

UNITED STATES AND PUERTO RICO
Schering-Plough will undertake Bayer's marketing and sales activities in the
United States and Puerto Rico for all of its primary care products, including
AVELOX and CIPRO in the antibiotics category, the cardiovascular product ADALAT
(nifedipine) and some other smaller, established primary care Bayer products.
Schering-Plough will pay Bayer a substantial royalty based on net sales of these
products. Schering-Plough will also undertake Bayer's U.S. commercialization
activities for



the erectile dysfunction medicine LEVITRA under Bayer's existing
global co-promotion agreement and will jointly manage the business in the United
States with GlaxoSmithKline PLC. Schering-Plough and Bayer will share Bayer's
portion of the profits on the U.S. sales of LEVITRA. A substantial number of
high-performing Bayer sales representatives and marketing personnel are expected
to be integrated into Schering-Plough's pharmaceutical organization in the
United States and Puerto Rico.
     AVELOX (oral and IV formulations) is a broad-spectrum, fast-acting
fluoroquinolone antibiotic for certain respiratory and skin infections. CIPRO
(BID, XR and IV formulations) is a broad-spectrum, fluoroquinolone antibiotic
approved for certain respiratory, skin, urinary tract and other infections. In
the United States, Schering-Plough will market these products alongside its own
products, including NASONEX(R) (mometasone furoate monohydrate), CLARINEX(R)
(desloratadine) and FORADIL(R) AEROLIZER(R) (formoterol fumarate inhalation
powder) in the allergy/respiratory category and VYTORIN(R)
(ezetimibe/simvastatin) and ZETIA in the cardiovascular category. In terms of
effective use of field force resources, the respiratory and anti-infective
product lines are seasonal and thus highly complementary to one another.
     The agreement with Bayer potentially restricts Schering-Plough from
marketing products in the United States that would compete with Bayer's
quinolone antibiotic AVELOX. As previously announced on June 22, 2004,
Schering-Plough and Toyama Chemical Co. Ltd. entered into a definitive licensing
agreement for garenoxacin, Toyama's proprietary quinolone antibacterial agent.
As a result of the agreement with Bayer, Schering-Plough expects it may need to
sublicense rights to the Toyama product in the United States. The company is
exploring its options with regard to garenoxacin and will continue to fulfill
its commitments to Toyama under its arrangement, including taking the product
through regulatory approval.

JAPAN
In Japan, the Schering-Plough and Bayer local organizations will co-market
Schering-Plough's novel cholesterol absorption inhibitor ZETIA, once approved
for distribution, while remaining functionally independent. ZETIA is currently
under regulatory review in Japan. The agreement does not include rights to any
future ZETIA combination products in Japan.

ONCOLOGY
Concurrent with today's announcement, Bayer said it plans to build a global
oncology business. The agreement with Bayer provides for Bayer to promote
certain Schering-Plough cancer products in the United States and key European
markets for a defined period of time, supplementing efforts by Schering-Plough's
oncology sales force.

     Schering-Plough is a global science-based health care company with leading
prescription, consumer and animal health products. Through internal research and
collaborations with partners, Schering-Plough discovers, develops, manufactures
and markets advanced drug therapies to meet important medical needs.



Schering-Plough's vision is to earn the trust of the physicians, patients and
customers served by its more than 30,000 people around the world. The company is
based in Kenilworth, N.J., and its Web site is www.schering-plough.com.
     DISCLOSURE NOTICE: This press release contains "forward-looking statements"
within the meaning of the Securities Litigation Reform Act of 1995, including
the potential strategic benefits and potential financial impact of the strategic
agreement with Bayer. Forward-looking statements relate to expectations or
forecasts of future events and not to historical information. Schering-Plough
does not assume the obligation to update any forward-looking statement. There
are no guarantees about the timing of implementation of the strategic agreement,
the results of the strategic agreement, the performance of Schering-Plough stock
or the performance of Schering-Plough's business. Actual results may vary
materially from forward-looking statements made here or in other Schering-Plough
written or spoken communications due to many factors and uncertainties, which
include the market acceptance of ZETIA in Japan, trade buying patterns for all
products covered by the strategic agreement ("covered products"), the
introduction and performance of products competitive to the covered products,
legislation that may impact the pricing/availability of the covered products and
other items impacting Schering-Plough, the pharmaceutical industry, and business
generally, all as discussed in Schering-Plough's Securities and Exchange
Commission filings, including the 2004 second quarter 10-Q and future SEC
filings.

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