September 14, 1999


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

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

         We have examined the Registration  Statement on Form S-8 to be filed by
you with the Securities and Exchange  Commission on or about  September 14, 1999
(the  "Registration  Statement") in connection with the  registration  under the
Securities  Act of 1933, as amended,  of an aggregate of 600,000  shares of your
Common Stock, par value $0.001 par value, under the Amended 1992 Incentive Stock
Plan.  Such shares of Common Stock are referred to herein as the  "Shares",  and
such plan is  referred to herein as the "Plan".  As your  counsel in  connection
with this  transaction,  we have examined the proceedings taken and are familiar
with the proceedings proposed to be taken by you in connection with the issuance
and sale of the Shares pursuant to the Plan.

         It is our opinion  that,  upon  issuance  and sale of the Shares in the
manner described in the Plan and pursuant to the agreements which accompany each
grant under the Plan,  and delivery of and payment for the Shares in  accordance
with the Plan and such grant agreements,  for a purchase price not less than the
par value of the  Shares,  such Shares will be validly  issued,  fully-paid  and
non-assessable.

         We consent to the use of this opinion as an exhibit to the Registration
Statement,  and further consent to the use of our name wherever appearing in the
Registration Statement and any amendments thereto.

                                                     Very truly yours,



                                                     Latham & Watkins