EXHIBIT 5.1

                                  [LETTERHEAD]


                                October 15, 2001

Barr Laboratories, Inc.
Two Quaker Road
P.O. Box D 2900
Pomona, New York 10970-0519

Beta Merger Sub I, Inc.
Two Quaker Road
P.O. Box D 2900
Pomona, New York 10970-0519

Ladies and Gentlemen:

            We have acted as counsel to Barr Laboratories, Inc., a New York
corporation (the "Company"), and Beta Merger Sub I, Inc., a Delaware corporation
and wholly-owned subsidiary of the Company ("Merger Sub"), in connection with
the filing with the Securities and Exchange Commission (the "Commission") of the
Company's registration statement on Form S-4 (the "Registration Statement") to
register additional shares of the Company's common stock, par value $0.01 per
share (the "Common Stock"), pursuant to Rule 462(b) under the Securities Act of
1933, as amended (the "Act"), in connection with the merger (the "Merger") of
Merger Sub with and into Duramed Pharmaceuticals, Inc., a Delaware corporation
("Duramed"), pursuant to the terms of that certain Agreement and Plan of Merger,
dated as of June 29, 2001, by and among the Company, Merger Sub and Duramed (the
"Merger Agreement").

            This opinion letter is delivered in accordance with the requirements
of Item 601(b)(5) of Regulation S-K under the Act.

            As such counsel and in connection with this opinion letter, we have
examined and are familiar with originals or copies, certified or otherwise
identified to our satisfaction, of (i) the Registration Statement, (ii) the
Composite Restated Certificate of Incorporation of the Company and the
Certificate of Incorporation of Merger Sub, each as currently in effect, (iii)
the By-Laws of the Company and Merger Sub, as currently in effect, (iv)
resolutions adopted by the Board of Directors of the Company and Merger Sub
relating to the issuance of the Common Stock in connection with the Merger and
the filing of the Registration Statement, and (v) the Merger Agreement. In
addition, we have examined, and have relied as to matters of fact upon,
originals or copies, certified or otherwise identified to our satisfaction, of
such corporate records,


Barr Laboratories, Inc.
Beta Merger Sub I, Inc.
October 15, 2001
Page 2

agreements, documents and other instruments and such certificates or comparable
documents of public officials and officers and representatives of the Company,
and have made such other and further investigations as we have deemed relevant
and necessary as a basis for the opinions hereinafter set forth.

            In rendering the opinion expressed below, we have assumed the legal
capacity of all natural persons, that the signatures of persons signing all
documents in connection with which this opinion letter is rendered are genuine,
that all documents submitted to us as originals or duplicate originals are
authentic and that all documents submitted to us as copies, whether certified or
not, conform to authentic original documents.

            Based on such examination and review, and subject to the
qualifications and limitations stated herein, we are of the opinion that the
additional shares of Common Stock to be issued in connection with the Merger,
when issued in accordance with the terms of the Merger Agreement, will be duly
and validly authorized and, when executed, delivered and issued in accordance
with the Merger Agreement, will be duly and validly issued, fully paid, and
non-assessable.

            Our opinion expressed above is subject to the qualifications that we
express no opinion as to the applicability of, compliance with, or effect of (i)
any bankruptcy, insolvency, reorganization, fraudulent transfer, fraudulent
conveyance, moratorium or other similar law affecting the enforcement of
creditors' rights generally, (ii) general principles of equity (regardless of
whether enforcement is considered in a proceeding in equity or at law), and
(iii) public policy considerations that may limit the rights of parties to
obtain certain remedies.

            We are members of the Bar of the State of New York, and the
foregoing opinion is limited to the law of the State of New York, the General
Corporation Law of the State of Delaware, and the federal law of the United
States of America.

            This opinion letter is rendered solely for the benefit of the
addressees hereof in connection with the consummation of the transactions
contemplated by the Merger Agreement. This opinion letter may not be relied upon
for any other purpose, or relied upon by, or furnished to, any other person,
firm or corporation or governmental agency without our prior written consent.

            We hereby consent to the filing of this opinion letter as an exhibit
to the Registration Statement and any amendments thereto. We also consent to the
reference to our name under the caption "Legal Matters" in the prospectus
contained in Registration Statement No. 333-66986, which was filed with the
Commission on August 6, 2001, subsequently amended on September 7, 2001 and
declared effective on September 11, 2001. The final prospectus was filed with
the Commission on September 24, 2001. In giving this consent, we do not hereby
admit that we are in the category of persons whose consent is required under
Section 7 of the Act or the rules and regulations of the Commission.

                                    Very truly yours,

                                    /s/ WINSTON & STRAWN