EXHIBIT 32.2

  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, Richard J. Klein, Chief Financial 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 March 31, 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: April 21, 2004

                                       /s/ Richard J. Klein
                                       -----------------------------------------
                                       Richard J. Klein
                                       Chief Financial Officer