EXHIBIT 32.1

      CERTIFICATION PURSUANT TO RULE 13A-14(b) OR RULE 15D-14(b) OF THE
      SECURITIES EXCHANGE ACT OF 1934 AND U.S.C. SECTION 1350

I, Michael A. Martino, President and Chief Executive Officer of Sonus
Pharmaceuticals, Inc. (the "Company"), certify, pursuant to Rule 13a-14(b) or
Rule 15d-14(b) of the Securities Exchange Act of 1934 and 18 U.S.C. Section
1350, that:

(1)   the Quarterly Report on Form 10-Q of the Company for the quarterly period
      ended June 30, 2004 (the "Report") fully complies with the requirements of
      Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C.
      78m or 780(d)); and

(2)   the information contained in the Report fairly presents, in all material
      respects, the financial condition and results of operations of the
      Company.

Dated: August 16, 2004

                                           /s/ Michael A. Martino
                                           -------------------------------------
                                           Michael A. Martino
                                           President and Chief Executive Officer