Exhibit 5.1
                                Latham & Watkins
                        12626 High Bluff Drive, Suite 300
                           San Diego, California 92130
                                 (858) 523-5400

March 15, 2001

Neurocrine Biosciences, Inc.
10555 Science Center Drive
San Diego, California 92121

Re:      Form S-8 Registration Statement

Ladies and Gentlemen:

                  In connection with the registration by Neurocrine Biosciences,
Inc., a Delaware corporation (the "Company"), of 750,000 shares of common stock,
par value $0.001 per share (the "Shares"),  of the Company to be issued pursuant
to the  Neurocrine  Biosciences,  Inc. 2001 Stock Option Plan (the "Plan") under
the Securities Act of 1933, as amended (the "Act"), on a Registration  Statement
on Form S-8 filed with the Securities and Exchange  Commission on March 15, 2001
(as amended from time to time, the "Registration Statement"), you have requested
our opinion with respect to the matters set forth below.

                  In our  capacity  as your  counsel  in  connection  with  such
registration,  we are  familiar  with the  proceedings  taken and proposed to be
taken by the Company in connection with the authorization,  issuance and sale of
the Shares, and for the purposes of this opinion,  have assumed such proceedings
will be timely completed in the manner presently proposed.  In addition, we have
made such legal and factual examinations and inquiries, including an examination
of originals or copies certified or otherwise  identified to our satisfaction of
such documents,  corporate records and instruments,  as we have deemed necessary
or appropriate for purposes of this opinion.

                  In our  examination,  we have assumed the  genuineness  of all
signatures,  the authenticity of all documents submitted to us as originals, and
the conformity to authentic original documents of all documents  submitted to us
as copies.

                  We  are  opining  herein  as to  the  effect  on  the  subject
transaction only of the General Corporation Law of the State of Delaware, and we
express no opinion  with  respect to the  applicability  thereto,  or the effect
thereon, of any other laws, or as to any matters of municipal law or the laws of
any other local agencies within the state.

                  Subject to the  foregoing,  it is our  opinion  that as of the
date hereof, the Shares have been duly authorized, and, upon the issuance of and
payment for the Shares in accordance  with the terms set forth in the Plan,  the
Shares will be validly issued, fully paid and nonassessable.

                  We consent to your  filing  this  opinion as an exhibit to the
Registration Statement.

                                                Very truly yours,

                                                /s/ LATHAM & WATKINS