EXHIBIT 5.1
                            GIBSON, DUNN & CRUTCHER LLP
                                  Jamboree Center
                             4 Park Plaza, Suite 1700
                             Irvine, California 92614

                                 January 25, 2002







(949) 451-3800


La Jolla Pharmaceutical Company
6455 Nancy Ridge Drive
San Diego, California  92121

        Re:    Registration Statement on Form S-3

Ladies and Gentlemen:

        We refer to the registration statement on Form S-3 (the "Registration
Statement") filed by La Jolla Pharmaceutical Company, a Delaware corporation
(the "Company"), with the Securities and Exchange Commission (the "Commission")
on the date hereof in connection with the registration under the Securities Act
of 1933, as amended (the "Securities Act") of 7,000,000 shares of common stock
of the Company, par value $0.01 per share (the "Shares").

        For purposes of rendering this opinion, we have examined the originals
or copies identified to our satisfaction as being true and complete copies of
such corporate records, certificates of officers of the Company or public
officials and such other documents, and have made such other factual and legal
investigations, as we have deemed relevant, necessary or appropriate. In such
examination, we have assumed the genuineness of all signatures, the conformity
to original documents of all documents submitted to us as conformed or
photostatic copies and the authenticity of the originals of such copies. With
respect to agreements and instruments executed by natural persons, we have
assumed the legal competency and authority of such persons. As to facts material
to the opinion expressed herein which were not independently established or
verified by us, we have relied upon oral or written statements and
representations of the Company and others.

        Based on our examination described above, subject to the assumptions
stated herein and relying on the statements of fact contained in the documents
that we have examined, it is our opinion that the Shares have been validly
issued, and are fully paid and nonassessable.

        We render no opinion herein as to matters involving the laws of any
jurisdiction other than (i) the federal laws of the United States of America;
(ii) the laws of the State of California; and (iii) the



La Jolla Pharmaceutical Company
January 25, 2002

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Delaware General Corporation Law (the "DGCL"). We are not admitted to practice
in the State of Delaware; however, we are generally familiar with the DGCL as
currently in effect and have made such inquiries as we consider necessary to
render the opinions contained in herein. This opinion is limited to the effect
of the current state of the laws of the United States of America, the State of
California and, to the limited extent set forth above, the State of Delaware and
to the current judicial interpretations thereof and to the facts bearing upon
this opinion as they currently exist. We assume no obligation to revise or
supplement this opinion in the event of future changes in such laws or the
interpretations thereof or such facts.

        We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement, and we further consent to the use of our name under the
caption, "Legal Matters" in the Prospectus forming a part of said Registration
Statement. In giving this consent, we do not thereby admit that we are within
the category of persons whose consent is required under Section 7 of the
Securities Act or the Rules and Regulations of the Commission.

                                            Very truly yours,

                                            /s/ GIBSON, DUNN & CRUTCHER LLP

                                            Gibson, Dunn & Crutcher LLP