EXHIBIT 5.1

                                 July 12, 2000

(415) 393-8200                                                     C 89349-00005

Silicon Valley Bancshares
3003 Tasman Drive
Santa Clara, CA 95054

    Re:  Registration Statement on Form S-3
       REGISTRATION NO. 333-39728

Ladies and Gentlemen:

    We have acted as counsel for Silicon Valley Bancshares, a Delaware
corporation (the "Company"), in connection with the registration by the Company
of shares of the Company's Common Stock, $0.001 par value per share (the "Common
Stock"), pursuant to the above-referenced Registration Statement on Form S-3
(the "Registration Statement") under the Securities Act of 1933, as amended (the
"Act"). The Company proposes to issue and sell up to 2,300,000 shares of Common
Stock (the "Shares") to a group of underwriters (the "Underwriters"), including
Merrill Lynch, Pierce Fenner & Smith Incorporated, Dain Rauscher Incorporated,
and Donaldson, Lufkin and Jenrette Securities Corporation, for offering to the
public.

    For the purpose of the opinion set forth below, we have examined and are
familiar with the proceedings taken and proposed to be taken by the Company in
connection with the authorization and issuance of the Shares, including, among
other things, such corporate records of the Company and certificates of officers
of the Company and of public officials and such other documents as we have
deemed relevant and necessary as the basis for the opinion set forth below. In
such examination, we have assumed the genuineness of all signatures, the
authenticity of all documents submitted to us as originals, the conformity to
the originals of all documents submitted to us as certified or photostatic
copies and the authenticity of the originals of such copies.

    On the basis of such investigation as we have deemed necessary, we are of
the opinion that (i) the Shares have been duly authorized, and (ii) when issued
and sold pursuant to the Registration Statement and in accordance with the terms
of the purchase agreement between the Company and the Underwriters,
substantially in the form filed as an exhibit to the Registration Statement, the
Shares will be validly issued, fully paid and nonassessable.

    The Company is a Delaware corporation. We are not admitted to practice in
Delaware. However, we are familiar with the Delaware General Corporation Law and
have made such review thereof as we consider necessary for the purpose of this
opinion. Therefore, this opinion is limited to the current laws of the State of
Delaware and the State of California, and to the current federal laws of the
United States of America.

    We 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 Registration Statement and the prospectus which forms a
part thereof. In giving these consents, 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,
                                          GIBSON, DUNN & CRUTCHER LLP