EXHIBIT 23.8

                   CONSENT OF SG COWEN SECURITIES CORPORATION

November 25, 2002


Board of Directors
Variagenics, Inc.
60 Hampshire Street
Cambridge, MA  02139

We hereby consent to the inclusion of our opinion, dated November 8, 2002, in
the joint proxy statement/prospectus (the "Prospectus") of Hyseq, Inc. attached
as Annex D which is a part of the Registration Statement on Form S-4 (the
"Registration Statement") and to the references to our firm in the Prospectus
under the headings "Summary" and "The Merger--Background of the Merger,"
"--Reasons for the Merger - Variagenics" and "--Opinion of SG Cowen Securities
Corporation".

In executing this consent, we do not admit or acknowledge that SG Cowen
Securities Corporation is within the class of persons whose consent is required
by Section 7 of the Securities Act of 1933, as amended, or the rules and
regulations promulgated thereunder, and we do not thereby admit that we are
experts with respect to any part of the Registration Statement under the meaning
of the term "expert" as used in the Securities Act of 1933, as amended, or the
rules and regulations promulgated thereunder.

Very truly yours,

/s/ SG COWEN SECURITIES CORPORATION

SG COWEN SECURITIES CORPORATION