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                                                                   Exhibit 10.40


February 3, 2000


SONUS Pharmaceuticals, Inc.                 VIA Telefax: (425) 489-0626
22026 20th Avenue, S.E., Suite 102          VIA Federal Express
Bothell, Washington 98021

Attention: Michael Martino, President and CEO

Dear Mike:

     This letter is in response to your letter dated February 2, 2000 proposing
modifications to certain agreements between Abbott and Sonus. We incorporated
many of your requested revisions to our proposal of earlier today and are
responding with the following counter-proposal. This counter-proposal is
presented in an effort to resolve a number of disputes between Abbott and Sonus.

U.S. MARKETING AGREEMENT

1.   Our counter-proposal serves to modify and amend the terms of: (a) the
Agreement between Abbott Laboratories ("Abbott") and SONUS Pharmaceuticals, Inc.
("Sonus") dated May 14, 1996, as amended by the First Amendment to Agreement
dated January 31, 1999 whereby Sonus granted to Abbott certain rights to
EchoGen(R) (the "Product"), and the accompanying Trademark License Agreement
dated May 14, 1996 and the letter agreement dated May 14, 1996 (together, the
"Marketing Agreement"); and (b) the Securities Purchase Agreement dated January
31, 1999 (the "Securities Purchase Agreement, and together with the Marketing
Agreement, the "Agreements").

2.   Notwithstanding the terms of the Agreements with respect to payment or
accrual of milestone payments, Abbott shall have until March 31, 2000 to review
all data with respect to the Product and, if applicable, the FDA approval
package for the Product. During the period of time beginning on the date of this
letter until March 31, 2000 ("Option Period"), Abbott shall have no obligation
to make any milestone payments or begin marketing or sales activities for the
Product and no milestone payments shall accrue during the Option Period.

3.   Abbott shall have the option, exercisable in its sole discretion by
providing written notice to Sonus on or before March 31, 2000, either to: (a)
terminate the Marketing Agreement, effective immediately, without cause and to
surrender all rights to the Product to Sonus, with no obligation to make any
milestone payments, whether or not accrued, or other future payments to Sonus;
or (b) negotiate in good faith to amend and restate the Marketing Agreement and
execute such amended and restated Marketing Agreement by

* Confidential portions omitted and
  filed separately with the SEC.

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April 30, 2000 to provide for a commercial arrangement mutually acceptable to
both Sonus and Abbott. Until such time as the Marketing Agreement is amended and
restated as set forth in paragraph 3(b), Abbott shall have no obligation to make
any milestone payments, whether or not accrued, or other future payments or to
market or sell the Product and no milestone payments shall accrue during the
Option Period.

4.   In the event that an amended and restated Marketing Agreement is not
executed on or prior to April 30, 2000, the Marketing Agreement shall terminate
on April 30, 2000, with no obligation to make any milestone payments, whether or
not accrued, or other future payments to Sonus.

5.   In the event that either: (a) Abbott elects to terminate the Marketing
Agreement pursuant to paragraph 3(a); or (b) the Marketing Agreement is
terminated pursuant to paragraph 4, then Abbott shall transfer to Sonus
training, marketing and sales materials and information relating to the
marketing, sale and distribution of the Product at no further cost to Sonus.

DEVELOPMENT AND SUPPLY AGREEMENT

6.   With respect to the QW3600 Contrast Agent Development and Supply Agreement
dated May 6, 1993, as amended by: (a) an Amendment dated August 22, 1995; (b)
Amendment 1 dated May 29, 1999; and (c) Amendment 2 dated May 15, 1997
(together, the "Supply Agreement"), Abbott and Sonus shall use their good faith
reasonable best efforts to negotiate and execute an amended and restated Supply
Agreement on or before March 31, 2000.

7.   Abbott will agree to develop and manufacture the Product *

8.   Notwithstanding the foregoing or the terms of the Supply Agreement, in the
event that Abbott terminates the Marketing Agreement pursuant to paragraph 3(a)
above or the Marketing Agreement terminates pursuant to paragraph 4, Abbott
shall manufacture the Product for a period of up to two (2) years following FDA
approval of the Product, but in no event later than July 1, 2002 (the
"Manufacturing Period"), unless Abbott and Sonus agree in writing to mutually
acceptable terms under which Abbott would continue to manufacture the Product.
After the Manufacturing Period, the Supply Agreement shall no longer be in force
and effect and Abbott shall have no obligation to manufacture the Product for
Sonus. During the Manufacturing Period, Abbott shall assist in the transfer of
manufacturing processes and data to Sonus or a third party selected by Sonus to
manufacture the Product.

9.   Beginning on the date of execution of this letter and until the earlier of:
(a) two (2) years following FDA approval; or (b) July 1, 2002, Abbott shall use
reasonable commercial efforts to manufacture Product in accordance with the
terms of the Supply Agreement. Abbott will consult with Sonus and allow Sonus
reasonable access to manufacturing records and personnel for purposes of
complying with the Product regulatory approval process in accordance with the
terms of the Supply Agreement.

Except as set forth in this letter, all rights and obligations of Abbott and
Sonus shall remain in effect.

* Confidential portions omitted and
  filed separately with the SEC.

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If you are in agreement with the foregoing, please so indicate by executing two
(2) copies of this letter in the space provided below. Please fax a signed copy
and return one original via Federal Express. Your signature below shall
constitute an affirmation that all requisite approvals necessary have been
obtained to execute this letter which shall constitute a binding agreement
between the parties. Abbott hereby confirms that it has received any and all
corporate authorizations to execute and deliver this letter.

Sincerely,

/s/ Richard A. Gonzalez
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Richard A. Gonzalez
President, Hospital Products Division
Abbott Laboratories


Accepted and agreed:

/s/ Michael Martino
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Michael Martino
President & CEO
Sonus Pharmaceuticals, Inc.




* Confidential portions omitted and
  filed separately with the SEC.