[BROBECK, PHLEGER & HARRISON LLP LETTERHEAD]

May 10, 2002



Com21, Inc.
750 Tasman Drive
Milpitas, CA  95035

Re:  Com21, Inc. Registration Statement on Form S-3 for Resale of
     350,000 Shares of Common Stock

Ladies and Gentlemen:

        We have acted as counsel to Com21, Inc., a Delaware corporation (the
"Company"), in connection with the registration for resale of 350,000 shares of
the Company's Common Stock (the "Shares"), as described in the Company's
Registration Statement on Form S-3 ("Registration Statement") filed with the
Securities and Exchange Commission under the Securities Act of 1933, as amended
(the "Act") as of May 10, 2002.

        This opinion is being furnished in accordance with the requirements of
Item 16 of Form S-3 and Item 601(b)(5)(i) of Regulation S-K.

        We have reviewed the Company's charter documents, the corporate
proceedings taken by the Company in connection with the original issuance and
sale of the Shares such other documents and records as we have deemed necessary
and relevant for the purposes hereof. In addition, we have relied on
certificates of officers of the Company and certificates of public officials as
to certain matters of fact relating to this opinion and have made such
investigations of law as we have deemed necessary and relevant as a basis
hereof. We have assumed the genuineness of all signatures, the authenticity of
all documents, certificates and records submitted to us as originals, the
conformity to authentic original documents, certificates and records of all such
documentation submitted to us as copies and the truthfulness of all statements
of facts contained therein. Based on such review, we are of the opinion that the
Shares, when issued and sold in the manner described in the Registration
Statement, will be validly issued, fully paid and nonassessable shares of Common
Stock.

        We consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement and to the reference to this firm under the caption
"Legal Matters" in the prospectus which is part of the Registration Statement.
In giving this consent, we do not thereby admit that we are within the category
of persons whose consent is required under Section 7 of the Act, the rules and
regulations of the Securities and Exchange Commission promulgated thereunder, or
Item 509 of Regulation S-K.

        The foregoing opinion is based on and limited to the General Corporation
Law of the State of Delaware and the relevant federal laws of the United States,
and we express no opinion with respect to the laws of any other jurisdiction.

        This opinion letter is rendered as of the date first written above and
we disclaim any obligation to advise you of facts, circumstances, events or
developments which hereafter may be brought to our attention and which may
alter, affect or modify the opinion expressed herein. Our opinion is expressly
limited to the matters set forth above and we render no opinion, whether by
implication or otherwise, as to any other matters relating to the Company or the
Shares.

                                              Very truly yours,

                                             /s/ BROBECK, PHLEGER & HARRISON LLP

                                              BROBECK, PHLEGER & HARRISON LLP