EXHIBIT 5.1



                                         August 10, 2005


Genelabs Technologies, Inc.
505 Penobscot Drive
Redwood City, California 94063

Re:      Genelabs Technologies, Inc.
         Form S-8 Registration Statement
         -------------------------------

Ladies and Gentlemen:

         We have acted as special counsel to Genelabs Technologies, Inc., a
California corporation (the "Company"), in connection with the registration of
(i) 4,000,000 shares (the "Option Shares") of common stock of the Company, no
par value per share (the "Common Stock"), issuable under the Company's 2001
Stock Option Plan (the "Stock Option Plan") and (ii) 2,000,000 shares (together
with the Option Shares, the "Shares") of Common Stock issuable under the
Company's 2001 Employee Stock Purchase Plan (the "Stock Purchase Plan" and
together with the Stock Option Plan, the "Plans").

         This opinion is being furnished in accordance with the requirements
of Item 601(b)(5) of Regulation S-K under the Securities Act of 1933, as
amended (the "Act").

         In connection with this opinion, we have examined originals or
copies, certified or otherwise identified to our satisfaction, of (i) the
Company's Registration Statement on Form S-8 (the "Registration Statement") to
be filed by the Company with the Securities and Exchange Commission (the
"Commission") on the date hereof; (ii) a specimen certificate representing the
Common Stock; (iii) the Amended and Restated Certificate of Incorporation of
the Company, as presently in effect; (iv) the Amended and Restated Bylaws of
the Company, as presently in effect; (v) the Plans; and (vi) certain
resolutions of the Board of Directors of the Company relating to the issuance
and sale of the Shares and related matters. We have also examined originals or
copies, certified or otherwise identified to our satisfaction, of such records
of the Company and such agreements, certificates of public officials,
certificates of officers or other representatives of the Company and others,
and such other documents, certificates and records as we have deemed necessary
or appropriate as a basis for the opinions set forth herein.

         In our examination, we have assumed the legal capacity of all natural
persons, the genuineness of all signatures, the authenticity of all documents
submitted to us as originals, the conformity to original documents of all
documents submitted to us as certified, conformed or photostatic copies and
the authenticity of the originals of such latter documents. In making our
examination of documents executed or to be executed by parties other than the
Company, we have assumed that such parties had or will have the power,
corporate or other, to enter into and perform all obligations thereunder, and
we have also assumed the due authorization by all requisite action, corporate
or other, and execution and delivery by such parties of such documents and the
validity and binding effect thereof. As to any facts material to the opinions
expressed herein that we have not independently established or verified, we
have relied upon statements and representations of officers and other
representatives of the Company and others.

         We have also assumed that each award agreement setting forth the
terms of each grant of options or other awards under the Plans is consistent
with the respective Plan and has been duly authorized and validly executed and
delivered by the parties thereto.

         We do not express any opinion as to the laws of any jurisdiction
other than the corporate laws of the State of California, and we do not
express any opinion as to the effect of any other laws on the opinion stated
herein.

         Based upon and subject to the foregoing, we are of the opinion that
when (i) the Registration Statement becomes effective under the Act; (ii)
certificates representing the Shares to be issued under the Plans in the form
of the specimen certificate examined by us have been manually signed by an
authorized officer of the transfer agent and registrar for the Common Stock
and registered by such transfer agent and registrar, and such certificates
have been delivered and paid for in accordance with the terms and conditions
of the Plan, the issuance and sale of such Shares will have been duly
authorized, and such Shares will be validly issued, fully paid and
nonassessable.

         We hereby consent to the filing of this opinion with the Commission
as Exhibit 5.1 to the Registration Statement. In giving this consent, we do
not thereby admit that we are included 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/ Skadden, Arps, Slate, Meagher & Flom LLP


San Francisco, California
August 10, 2005