EXHIBIT 5.1

                                  July 28, 2000

Kana Communications, Inc.
740 Bay Road
Redwood City, CA 94063

                  Re: Kana Communications, Inc. Registration Statement on
                      Form S-1 for 3,010,486 Shares of Common Stock

Ladies and Gentlemen:

     We have acted as counsel to Kana Communications, Inc., a Delaware
corporation (the "Company"), in connection with the proposed issuance and sale
by the Company of up to 3,010,486 shares of the Company's Common Stock (the
"Shares") pursuant to the Company's Registration Statement on Form S-1 (the
"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(a) of Form S-1 and Item 601(b)(5)(i) of Regulation S-K.

     We have reviewed the Company's charter documents and the corporate
proceedings taken by the Company in connection with the issuance and sale of the
Shares. Based on such review, we are of the opinion that the Shares have been
duly authorized, and if, as and when issued in accordance with the Registration
Statement and the related prospectus (as amended and supplemented through the
date of issuance) will be legally issued, fully paid and nonassessable.

     We consent to the filing of this opinion letter 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 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