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                                                                     EXHIBIT 5.1

                               September 10, 2001

Com21, Inc.
750 Tasman Drive
Milpitas, CA 95035

          Re:  Com21, Inc. Registration Statement on Form S-3 for Resale of -
               5,402,250 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 5,402,250
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").

          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, and a certificate of a Company officer regarding (among
other things) the Company's receipt of consideration upon the original
issuance and sale of the Shares. Based on such review, we are of the opinion
that the Shares are duly authorized, validly issued, fully paid and
nonassessable.

          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.

          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


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                                                              September 10, 2001
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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