<PAGE>

                                                                    Exhibit 10.2

                          REGISTRATION RIGHTS AGREEMENT

      This REGISTRATION RIGHTS AGREEMENT, dated as of May 7, 2004 (this
"Agreement"), is made by and among Sonus Pharmaceuticals, Inc., a Delaware
corporation, with headquarters located at 22026 20th Avenue S.E., Bothell,
Washington 98021 (the "Company"), and the investors named on the signature pages
hereto (the "Initial Investors").

                                    RECITALS:

      A.    In connection with the Securities Purchase Agreement dated May 7,
2004 between the Initial Investors and the Company (the "Purchase Agreement"),
the Company has agreed, upon the terms and subject to the conditions of the
Purchase Agreement, to issue and sell to the Initial Investors 2,900,000 shares
of the Company's Common Stock (the "Common Shares").

      B.    In order to induce the Initial Investors to execute and deliver the
Purchase Agreement, the Company has agreed to provide certain registration
rights under the Securities Act and applicable state securities laws with
respect to the Common Shares.

      In consideration of the premises and the mutual covenants contained herein
and other good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the Company and the Initial Investors hereby agree as
follows:

                                    ARTICLE I
                                   DEFINITIONS

      Capitalized terms used and not otherwise defined herein have the
respective meanings given them set forth in the Purchase Agreement. In addition,
as used in this Agreement, the following terms have the following meanings:

      1.1   "Closing Date" means the date on which the purchase of the Common
Shares is consummated pursuant to the Purchase Agreement.

      1.2   "Common Shares" means the shares of Common Stock sold pursuant to
the Purchase Agreement.

      1.3   "Investors" means the Initial Investors and any of their transferees
or assignees who agree to become bound by the provisions of this Agreement in
accordance with Article IX hereof.

      1.4   "Registrable Common Shares" means the Common Shares, and any shares
of capital stock issued or issuable from time to time (with any adjustments) in
exchange for or otherwise with respect to the Common Shares (including shares
issued pursuant to Section 2.2 hereof).

      1.5   "Registration Period" means the period between the date of this
Agreement and the earlier of (i) the date on which (x) all of the Registrable
Common Shares have been sold by the Investors pursuant to the Registration
Statement and (y) are freely tradable under the Securities Act

<PAGE>

(except that this clause (y) shall not apply with respect to Shares sold to
affiliates) and no further Registrable Common Shares may be issued in the
future, or (ii) the date on which all the Registrable Common Shares may be
immediately sold by the Investors without registration and without restriction
as to the number of Registrable Common Shares to be sold, pursuant to Rule 144
or otherwise.

      1.6   "Registration Statement" means a Registration Statement of the
Company filed under the Securities Act.

      1.7   The terms "register," "registered," and "registration" refer to a
registration effected by preparing and filing a Registration Statement or
statements in compliance with the Securities Act and pursuant to Rule 415 and
the declaration or ordering of effectiveness of such Registration Statement by
the SEC.

      1.8   "Rule 415" means Rule 415 under the Securities Act , or any
successor Rule providing for offering securities on a continuous basis, and
applicable rules and regulations thereunder.

      1.9   "Common Shares" means the Common Shares sold pursuant to the
Purchase Agreement.

                                   ARTICLE II
                                  REGISTRATION

      2.1   Mandatory Registration. The Company will file with the SEC a
Registration Statement on Form S-3 registering all of the Registrable Common
Shares for resale within 20 days after the Closing Date under the Purchase
Agreement. If Form S-3 is not available at that time, then the Company will file
a Registration Statement on such form as is then available to effect a
registration of all of the Registrable Common Shares, subject to the consent of
the Investors, which consent will not be unreasonably withheld. The Company
shall not permit any securities other than the Registrable Common Shares
purchased by the Investors to be included in the Registration Statement.

      2.2   Effectiveness of the Registration Statement. The Company will use
its best efforts to cause the Registration Statement to be declared effective by
the SEC as soon as practicable after filing, and in any event no later than the
90th day after the Closing Date (the "Required Effective Date"). The Company's
best efforts will include, but not be limited to, promptly responding to all
comments received from the staff of the SEC. If the Company receives
notification from the SEC that the Registration Statement will receive no
further action or review from the SEC, then the Company will cause the
Registration Statement to become effective within five business days after such
SEC notification. Once the Registration Statement is declared effective by the
SEC, the Company will cause the Registration Statement to remain effective
throughout the Registration Period, except as permitted under Section 3. On the
date of each monthly anniversary of the date on which any breach of Section 2.1
above or this Section 2.2 first occurs (including failure to file a Registration
Statement or to cause a Registration Statement to be declared effective within
the time periods set forth herein) until the applicable default is cured (each a
"Payment Date"), the Company shall pay to each Investor as damages 1.5% of the
purchase price paid by such Investor pursuant to the Purchase Agreement per
month, pro-rated for any period less than 30 days. Such payment shall be the
sole remedy to the Investors for the Company's default of this Section 2.2 and
shall be made

                                       2

<PAGE>

in shares of Common Stock, valued at the average closing sale prices of the
Company's Common Stock during five (5) trading days ending on the day prior to
the Payment Date, provided, that the total number of shares of the Company's
Common Stock payable pursuant to this Section 2.2 to any Investor shall not
exceed the lower of (i) the aggregate number of shares purchased pursuant to the
Purchase Agreement by such Investor and (ii) the number of shares, less one
share, which, if issued, would have, at the time of the Closing Date or the
Payment Date, required shareholder approval of such issuance pursuant to Section
4350(i)(1)(D) of the Nasdaq Marketplace Rules. In the event the number of shares
of the Company's Common Stock issuable under this Section 2.2 is restricted by
the limitations in the previous sentence, the balance of the damages payable by
the Company pursuant to this Section 2.2 shall be paid in cash on the applicable
Payment Date in accordance with payment instructions provided by each Investor.

      2.3   Piggyback Registrations.

            (a)   If, at any time prior to the expiration of the Registration
Period, the Registration Statement contemplated in Section 2.1 above is not
declared effective with respect to all of the Registrable Common Shares and the
Company decides to register any of its securities for its own account or for the
account of others, then the Company will promptly give the Investors written
notice thereof and will use its best efforts to include in such registration all
or any part of the Registrable Common Shares requested by such Investors to be
included therein (excluding any Registrable Common Shares previously included in
a Registration Statement which has been declared effective and has not been
withdrawn). This requirement does not apply to Company registrations on Form S-4
or S-8 or their equivalents relating to equity securities to be issued solely in
connection with an acquisition of any entity or business or equity securities
issuable in connection with stock option or other employee benefit plans. Each
Investor must give its request for registration under this paragraph to the
Company in writing within 15 days after receipt from the Company of notice of
such pending registration. If the registration for which the Company gives
notice is a public offering involving an underwriting, the Company will so
advise the Investors as part of the above-described written notice. In that
event, if the managing underwriter(s) of the public offering impose a limitation
on the number of shares of Common Stock that may be included in the Registration
Statement because, in such underwriter(s)' judgment, such limitation would be
necessary to effect an orderly public distribution, then the Company will be
obligated to include only such limited portion, if any, of the Registrable
Common Shares with respect to which such Investors have requested inclusion
hereunder. Any exclusion of Registrable Common Shares will be made pro rata
among all holders of the Company's securities seeking to include shares of
Common Stock in proportion to the number of shares of Common Stock sought to be
included by those holders. However, the Company will not exclude any Registrable
Common Shares unless the Company has first excluded all outstanding securities
the holders of which are not entitled by right to inclusion of such securities
in such Registration Statement or are not entitled pro rata inclusion with the
Registrable Common Shares. No registration rights that limit or subordinate the
rights of the Investors to register the Registrable Common Shares will be
granted by the Company until one or more registration statements covering all of
the Registrable Common Shares have become effective.

            (b)   No right to registration of Registrable Common Shares under
this Section 2.3 limits in any way the registration required under Section 2.1
above. The obligations of the Company under this Section 2.3 expire upon the
earlier of (i) the effectiveness of the Registration Statement filed pursuant to
Section 2.1 above, (ii) after the Company has afforded the opportunity for the
Investors to exercise registration rights under this Section 2.3 for two
registrations (provided, however, that any Investor that has had any Registrable
Common Shares excluded from any

                                       3

<PAGE>

Registration Statement in accordance with this Section 2.3 may include in any
additional Registration Statement filed by the Company the Registrable Common
Shares so excluded) or (iii) when all of the Registrable Common Shares held by
any Investor may be sold by such Investor under Rule 144 without being subject
to any volume restrictions.

      2.4   Eligibility to use Form S-3. The Company represents and warrants
that it meets the requirements for the use of Form S-3 for registration of the
sale by the Investors of the Registrable Common Shares. The Company will file
all reports required to be filed by the Company with the SEC in a timely manner
so as to preserve its eligibility for the use of Form S-3.

                                  ARTICLE III
                      ADDITIONAL OBLIGATIONS OF THE COMPANY

      3.1   Continued Effectiveness of Registration Statement. Subject to the
limitations set forth in Section 3.6, the Company will keep the Registration
Statement covering the Registrable Common Shares effective under Rule 415 at all
times during the Registration Period. In the event that the number of shares
available under a Registration Statement filed pursuant to this Agreement is
insufficient to cover all of the Registrable Common Shares issued, the Company
will (if permitted) amend the Registration Statement or file a new Registration
Statement (on the short form available therefor, if applicable), or both, so as
to cover all of the Registrable Common Shares. The Company will file such
amendment or new Registration Statement as soon as practicable, but in no event
later than 30 business days after the necessity therefor arises (based upon the
market price of the Common Stock and other relevant factors on which the Company
reasonably elects to rely). The Company will use its best efforts to cause such
amendment or new Registration Statement to become effective as soon as is
practicable after the filing thereof, but in no event later than 90 days after
the date on which the Company reasonably first determines the need therefor.

      3.2   Accuracy of Registration Statement. Any Registration Statement
(including any amendments or supplements thereto and prospectuses contained
therein) filed by the Company covering Registrable Common Shares will not
contain any untrue statement of a material fact or omit to state a material fact
required to be stated therein, or necessary to make the statements therein, in
light of the circumstances in which they were made, not misleading. The Company
will prepare and file with the SEC such amendments (including post-effective
amendments) and supplements to the Registration Statement and the prospectus
used in connection with the Registration Statement as may be necessary to permit
sales pursuant to the Registration Statement at all times during the
Registration Period, and, during such period, will comply with the provisions of
the Securities Act with respect to the disposition of all Registrable Common
Shares of the Company covered by the Registration Statement until the
termination of the Registration Period, or if earlier, until such time as all of
such Registrable Common Shares have been disposed of in accordance with the
intended methods of disposition by the seller or sellers thereof as set forth in
the Registration Statement.

      3.3   Furnishing Documentation. The Company will furnish to each Investor
whose Registrable Common Shares are included in a Registration Statement, or to
its legal counsel, (a) promptly after such document is filed with the SEC, one
copy of any Registration Statement filed pursuant to this Agreement and any
amendments thereto, each preliminary prospectus and final prospectus and each
amendment or supplement thereto provided, however, that not less than three (3)
Business Days prior to the filing of the Registration Statement or any related
Prospectus or any amendment or supplement thereto, the Company shall (i) furnish
to a single firm of legal counsel, designated by the Investors who hold a
majority of the Registrable Common Shares being sold

                                       4

<PAGE>

pursuant to a Registration Statement ("Investors' Counsel"), copies of all such
documents proposed to be filed, which documents (other than those incorporated
by reference) will be subject to the timely review of such Investors' Counsel,
and (ii) at the request of Investors' Counsel cause its officers and directors,
counsel and independent certified public accountants to respond to such
inquiries as shall be necessary, in the reasonable opinion of Investors'
Counsel, to conduct a reasonable investigation within the meaning of the
Securities Act. The Company shall not file the Registration Statement or any
such Prospectus or any amendments or supplements thereto to which Investors'
Counsel shall reasonably object in writing within three (3) Business Days of
their receipt thereof; and (b) a number of copies of a prospectus, including a
preliminary prospectus, and all amendments and supplements thereto, and such
other documents as the Investor may reasonably request in order to facilitate
the disposition of the Registrable Common Shares owned by the Investor. The
Company will promptly notify by facsimile or email each Investor whose
Registrable Common Shares are included in any Registration Statement of the
effectiveness of the Registration Statement and any post-effective amendment. In
the event of an objection by Investors' Counsel pursuant to this Section 3.3,
the period of time during which the Company must file a Registration Statement
pursuant to Article II shall be tolled until such objection is resolved,
provided that such toll period shall not exceed three (3) business days.

      3.4   Additional Obligations. The Company will use its best efforts to (a)
register and qualify the Registrable Common Shares covered by a Registration
Statement under such other securities or blue sky laws of such jurisdictions as
each Investor who holds (or has the right to hold) Registrable Common Shares
being offered reasonably requests, (b) prepare and file in those jurisdictions
any amendments (including post-effective amendments) and supplements to such
registrations and qualifications as may be necessary to maintain their
effectiveness during the Registration Period, (c) take any other actions
necessary to maintain such registrations and qualifications in effect at all
times during the Registration Period, and (d) take any other actions reasonably
necessary or advisable to qualify the Registrable Common Shares for sale in such
jurisdictions. Notwithstanding the foregoing, the Company is not required, in
connection with such obligations, to (i) qualify to do business in any
jurisdiction where it would not otherwise be required to qualify but for this
Section 3.4, (ii) subject itself to general taxation in any such jurisdiction,
(iii) file a general consent to service of process in any such jurisdiction,
(iv) provide any undertakings that cause material expense or material burden to
the Company, or (v) make any change in its charter or bylaws, which in each case
the Board of Directors of the Company determines to be contrary to the best
interests of the Company and its stockholders.

      3.5   Underwritten Offerings. If the Investors who hold a majority in
interest of the Registrable Common Shares being offered in an offering pursuant
to a Registration Statement or any amendment or supplement thereto under this
Agreement select underwriters reasonably acceptable to the Company for such
offering, the Company will enter into and perform its obligations under an
underwriting agreement in usual and customary form including, without
limitation, customary indemnification and contribution obligations, with the
managing underwriter of such offering.

                                       5

<PAGE>

      3.6   Suspension of Registration.

            (a)   The Company will notify (by telephone and also by facsimile
and reputable overnight courier) each Investor who holds Registrable Common
Shares being sold pursuant to a Registration Statement of the happening of any
event of which the Company has knowledge as a result of which the prospectus
included in the Registration Statement as then in effect includes an untrue
statement of a material fact or omits to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading. The Company will make
such notification as promptly as practicable (but in no event more than two
business days) after the Company becomes aware of the event, will promptly (but
in no event more than ten business days) prepare and file a supplement or
amendment to the Registration Statement to correct such untrue statement or
omission, and will deliver a number of copies of such supplement or amendment to
each Investor as such Investor may reasonably request.

            (b)   Notwithstanding the obligations under Section 3.6(a), if in
the good faith judgment of the Company, following consultation with legal
counsel, it would be detrimental to the Company and its stockholders for resales
of Registrable Common Shares to be made pursuant to the Registration Statement
due to the existence of a material development or potential material development
involving the Company which the Company would be obligated to disclose in the
Registration Statement, but which disclosure would be premature or otherwise
inadvisable at such time or would reasonably be expected to have a material
adverse effect upon the Company and its stockholders, the Company will have the
right to suspend the use of the Registration Statement for a period of not more
than forty-five days consecutively or in the aggregate in any twelve-month
period. If the Company suspends the Registration Statement for a period
exceeding that prescribed above, than the Company shall pay to each Investor as
damages 1.5% of the purchase price paid by such Investor pursuant to the
Purchase Agreement for Common Shares still held by such Investor, per month,
pro-rated for any period less than 30 days, until such suspension has been
cured. Such payment shall be the sole remedy to the Investors for the Company's
default of this Section 3.6(b).

            (c)   Subject to the Company's rights under this Section 3, the
Company will use its best efforts to prevent the issuance of any stop order or
other suspension of effectiveness of a Registration Statement and, if such an
order is issued, will use its best efforts to obtain the withdrawal of such
order at the earliest possible time and to notify each Investor that holds
Registrable Common Shares being sold (or, in the event of an underwritten
offering, the managing underwriters) of the issuance of such order and the
resolution thereof.

            (d)   Notwithstanding anything to the contrary contained herein or
in the Purchase Agreement, if the use of the Registration Statement is suspended
by the Company, the Company will promptly (but in no event more than two
business days) give notice of the suspension to all Investors whose securities
are covered by the Registration Statement, and will promptly (but in no event
more than two business days) notify each such Investor as soon as the use of the
Registration Statement may be resumed. Notwithstanding anything to the contrary
contained herein or in the Purchase Agreement, the Company will cause the
Transfer Agent to deliver unlegended shares of Common Stock to a transferee of
an Investor in accordance with the terms of the Purchase Agreement in connection
with any sale of Registrable Common Shares with respect to which such Investor
has entered into a contract for sale prior to receipt of notice of such
suspension and for which such Investor has not yet settled, unless otherwise
prohibited by law.

                                       6

<PAGE>

      3.7   Review by the Investors. In accordance with Section 3.3 above, the
sections of any such Registration Statement including information with respect
to the Investors, the Investors' beneficial ownership of securities of the
Company or the Investors' intended method of disposition of Registrable Common
Shares must conform to the information provided to the Company by each of the
Investors or Investors Counsel.

      3.8   Comfort Letter; Legal Opinion. At the request of the Investors who
hold a majority in interest of the Registrable Common Shares being sold pursuant
to a Registration Statement, and on the date that Registrable Common Shares are
delivered to an underwriter for sale in connection with the Registration
Statement, the Company will furnish to the Investors and the underwriters (i) a
letter, dated such date, from the Company's independent certified public
accountants, in form and substance as is customarily given by independent
certified public accountants to underwriters in an underwritten public offering,
addressed to the underwriters; and (ii) an opinion, dated such date, from
counsel representing the Company for purposes of the Registration Statement, in
form and substance as is customarily given in an underwritten public offering,
addressed to the underwriters and Investors.

      3.9   Due Diligence; Confidentiality.

            (a)   The Company will make available for inspection by any Investor
whose Registrable Common Shares are being sold pursuant to a Registration
Statement, any underwriter participating in any disposition pursuant to the
Registration Statement, and any attorney, accountant or other agent retained by
any such Investor or underwriter (collectively, the "Inspectors"), all pertinent
financial and other records, pertinent corporate documents and properties of the
Company (collectively, the "Records"), as each Inspector reasonably deems
necessary to enable the Inspector to exercise its due diligence responsibility.
The Company will cause its officers, directors and employees to supply all
information that any Inspector may reasonably request for purposes of performing
such due diligence.

            (b)   Each Inspector will hold in confidence, and will not make any
disclosure (except to an Investor) of, any Records or other information that the
Company determines in good faith to be confidential, and of which determination
the Inspectors are so notified, unless (i) the disclosure of such Records is
necessary to avoid or correct a misstatement or omission in any Registration
Statement, (ii) the release of such Records is ordered pursuant to a subpoena or
other order from a court or government body of competent jurisdiction, (iii) the
information in such Records has been made generally available to the public
other than by disclosure in violation of this or any other agreement (to the
knowledge of the relevant Inspector), (iv) the Records or other information was
developed independently by an Inspector without breach of this Agreement, (v)
the information was known to the Inspector before receipt of such information
from the Company, or (vi) the information was disclosed to the Inspector by a
third party without restriction. The Company is not required to disclose any
confidential information in the Records to any Inspector unless and until such
Inspector has entered into a confidentiality agreement (in form and substance
reasonably satisfactory to the Company) with the Company with respect thereto,
substantially in the substance of this Section 3.9(b). Each Investor will, upon
learning that disclosure of Records containing confidential information is
sought in or by a court or governmental body of competent jurisdiction or
through other means, give prompt notice to the Company and allow the Company, at
the Company's expense, to undertake appropriate action to prevent disclosure of,
or to obtain a protective order for, the Records deemed confidential. Nothing
herein will be deemed to limit the Investor's ability to sell

                                       7

<PAGE>

Registrable Common Shares in a manner that is otherwise consistent with
applicable laws and regulations.

            (c)   The Company will hold in confidence, and will not make any
disclosure of, information concerning an Investor provided to the Company under
this Agreement unless (i) disclosure of such information is necessary to comply
with federal or state securities laws, (ii) the disclosure of such information
is necessary to avoid or correct a misstatement or omission in any Registration
Statement, (iii) the release of such information is ordered pursuant to a
subpoena or other order from a court or governmental body of competent
jurisdiction, (iv) such information has been made generally available to the
public other than by disclosure in violation of this Agreement or any other
agreement, (v) the information was disclosed to the Company by a third party
without restriction or (vi) such Investor consents to the form and content of
any such disclosure. If the Company learns that disclosure of such information
concerning an Investor is sought in or by a court or governmental body of
competent jurisdiction or through other means, the Company will give prompt
notice to such Investor prior to making such disclosure and allow such Investor,
at its expense, to undertake appropriate action to prevent disclosure of, or to
obtain a protective order for, such information.

      3.10  Listing. The Company will (i) cause all of the Registrable Common
Shares covered by each Registration Statement to be listed on each national
securities exchange on which securities of the same class or series issued by
the Company are then listed, if any, if the listing of such Registrable Common
Shares is then permitted under the rules of such exchange, or (ii) to the extent
the securities of the same class or series are not then listed on a national
securities exchange, secure the designation and quotation of all of the
Registrable Common Shares covered by each Registration Statement on Nasdaq.

      3.11  Transfer Agent; Registrar. The Company will provide a transfer agent
and registrar, which may be a single entity, for the Registrable Common Shares
not later than the effective date of the Registration Statement.

      3.12  Share Certificates. The Company will cooperate with the Investors
who hold Registrable Common Shares being sold and with the managing
underwriter(s), if any, to facilitate the timely preparation and delivery of
certificates (not bearing any restrictive legends) representing Registrable
Common Shares to be offered pursuant to a Registration Statement and will enable
such certificates to be in such denominations or amounts as the case may be, and
registered in such names as the Investors or the managing underwriter(s), if
any, may reasonably request, all in accordance with Article V of the Purchase
Agreement.

      3.13  Plan of Distribution. At the request of the Investors holding a
majority in interest of the Registrable Common Shares registered pursuant to a
Registration Statement, the Company will promptly prepare and file with the SEC
such amendments (including post-effective amendments) and supplements to the
Registration Statement, and the prospectus used in connection with the
Registration Statement, as may be necessary in order to change the plan of
distribution set forth in such Registration Statement.

      3.14  Securities Laws Compliance. The Company will comply with all
applicable laws related to any Registration Statement relating to the offer and
sale of Registrable Securities and with all applicable rules and regulations of
governmental authorities in connection therewith (including,

                                       8

<PAGE>

without limitation, the Securities Act, the Exchange Act and the rules and
regulations promulgated by the SEC).

      3.15  Further Assurances. The Company will take all other reasonable
actions as any Investor or the underwriters, if any, may reasonably request to
expedite and facilitate disposition by such Investor of the Registrable Common
Shares pursuant to the Registration Statement.

                                   ARTICLE IV
                          OBLIGATIONS OF THE INVESTORS

      4.1   Investor Information. As a condition to the obligations of the
Company to complete any registration pursuant to this Agreement with respect to
the Registrable Common Shares of each Investor, such Investor will furnish to
the Company such information regarding itself, the Registrable Common Shares
held by it and the intended method of disposition of the Registrable Common
Shares held by it as is required by the SEC to effect the registration of the
Registrable Common Shares. At least five business days prior to the first
anticipated filing date of a Registration Statement for any registration under
this Agreement, the Company will notify each Investor of the information the
Company requires from that Investor if the Investor elects to have any of its
Registrable Common Shares included in the Registration Statement other than
information contained in the Investor Questionnaire attached hereto as Annex A,
which shall be completed and delivered to the Company no later than five (5)
days after the Closing Date. If, within two business days prior to the filing
date, the Company has not received the requested information from an Investor,
then the Company may file the Registration Statement without including
Registrable Common Shares of that Investor.

      4.2   Further Assurances. Each Investor will cooperate with the Company,
as reasonably requested by the Company, in connection with the preparation and
filing of any Registration Statement hereunder, unless such Investor has
notified the Company in writing of such Investor's election to exclude all of
such Investor's Registrable Common Shares from the Registration Statement.

      4.3   Suspension of Sales. Upon receipt of any notice from the Company of
the happening of any event of the kind described in Section 3.6, each Investor
will immediately discontinue disposition of Registrable Common Shares pursuant
to the Registration Statement covering such Registrable Common Shares until it
receives copies of the supplemented or amended prospectus contemplated by
Section 3.6. If so directed by the Company, each Investor will deliver to the
Company (at the expense of the Company) or destroy (and deliver to the Company a
certificate of destruction) all copies in the Investor's possession (other than
a limited number of file copies) of the prospectus covering such Registrable
Common Shares that is current at the time of receipt of such notice.

      4.4   Underwritten Offerings.

            (a)   If Investors holding a majority in interest of the Registrable
Common Shares being registered (with the approval of the Initial Investors)
determine to engage the services of an underwriter, each Investor will enter
into and perform such Investor's obligations under an underwriting agreement, in
usual and customary form, including, without limitation, customary
indemnification and contribution obligations, with the managing underwriter of
such offering, and

                                       9

<PAGE>

will take such other actions as are reasonably required in order to expedite or
facilitate the disposition of the Registrable Common Shares, unless such
Investor has notified the Company in writing of such Investor's election to
exclude all of its Registrable Common Shares from such Registration Statement.

            (b)   Without limiting any Investor's rights under Section 2.1
hereof, no Investor may participate in any underwritten distribution hereunder
unless such Investor (a) agrees to sell such Investor's Registrable Common
Shares on the basis provided in any underwriting arrangements approved by the
Investors entitled hereunder to approve such arrangements, (b) completes and
executes all questionnaires, powers of attorney, indemnities, underwriting
agreements and other documents reasonably required under the terms of such
underwriting arrangements, and (c) agrees to pay its pro rata share of all
underwriting discounts and commissions applicable with respect to its
Registrable Common Shares.

                                   ARTICLE V
                            EXPENSES OF REGISTRATION

      The Company will bear all reasonable expenses, other than underwriting
discounts and commissions, and transfer taxes, if any, incurred in connection
with registrations, filings or qualifications pursuant to Articles II and III of
this Agreement, including, without limitation, all registration, listing and
qualifications fees, printers and accounting fees, the fees and disbursements of
counsel for the Company, and the reasonable fees and disbursements of one firm
of legal counsel selected by the Initial Investors pursuant to Section 3.7
hereof.

                                   ARTICLE VI
                                 INDEMNIFICATION

      In the event that any Registrable Common Shares are included in a
Registration Statement under this Agreement:

      6.1   To the extent permitted by law, the Company will indemnify, defend
and hold harmless each Investor that holds such Registrable Common Shares, and
agents, employees, attorneys, accountants, underwriters (as defined in the
Securities Act) for such Investors and any directors or officers of such
Investor or such underwriter and any person who controls such Investor or such
underwriter within the meaning of the Securities Act or the Exchange Act (each,
an "Investor Indemnified Person") against any losses, claims, damages, expenses
or liabilities (collectively, and together with actions, proceedings or
inquiries by any regulatory or self-regulatory organization, whether commenced
or threatened in respect thereof, "Claims") to which any of them become subject
under the Securities Act, the Exchange Act or otherwise, insofar as such Claims
arise out of or are based upon any of the following statements, omissions or
violations in a Registration Statement filed pursuant to this Agreement, any
post-effective amendment thereof or any prospectus included therein: (a) any
untrue statement or alleged untrue statement of a material fact contained in the
Registration Statement or any post-effective amendment thereof or the omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading, (b) any
untrue statement or alleged untrue statement of a material fact contained in the
prospectus or any preliminary prospectus (as it may be amended or supplemented)
or the omission or alleged omission to state therein any material fact necessary
to make the statements made therein, in light of the circumstances under which
the statements therein were made, not misleading, or (c) any violation or
alleged violation by the Company of the Securities

                                       10

<PAGE>

Act, the Exchange Act or any other law, including without limitation any state
securities law or any rule or regulation thereunder (the matters in the
foregoing clauses (a) through (c) being, collectively, "Violations"). Subject to
the restrictions set forth in Section 6.4 with respect to the number of legal
counsel, the Company will reimburse the Investors and each such attorney,
accountant, underwriter or controlling person and each such other Investor
Indemnified Person, promptly as such expenses are incurred and are due and
payable, for any legal fees or other reasonable expenses incurred by them in
connection with investigating or defending any Claim. Notwithstanding anything
to the contrary contained herein, the indemnification agreement contained in
this Section 6.1 (i) does not apply to a Claim by an Investor Indemnified Person
arising out of or based upon a Violation that occurs in reliance upon and in
conformity with information furnished in writing to the Company by such Investor
Indemnified Person expressly for use in the Registration Statement or any such
amendment thereof or supplement thereto, if such prospectus or supplement
thereto was timely made available by the Company pursuant to Section 3.3 hereof;
and (ii) does not apply to amounts paid in settlement of any Claim if such
settlement is made without the prior written consent of the Company, which
consent will not be unreasonably withheld. This indemnity obligation will remain
in full force and effect regardless of any investigation made by or on behalf of
the Indemnified Persons and will survive the transfer of the Registrable Common
Shares by the Investors under Article IX of this Agreement.

      6.2   In connection with any Registration Statement in which an Investor
is participating, each such Investor will indemnify and hold harmless, to the
same extent and in the same manner set forth in Section 6.1 above, the Company,
each of its directors, each of its officers who signs the Registration
Statement, each person, if any, who controls the Company within the meaning of
the Securities Act or the Exchange Act, and any other stockholder selling
securities pursuant to the Registration Statement or any of its directors or
officers or any person who controls such stockholder within the meaning of the
Securities Act or the Exchange Act (each a "Company Indemnified Person") against
any Claim to which any of them may become subject under the Securities Act, the
Exchange Act or otherwise, insofar as such Claim arises out of or is based upon
any Violation, in each case to the extent (and only to the extent) that such
Violation occurs in reliance upon and in conformity with written information
furnished to the Company by such Investor expressly for use in such Registration
Statement. Subject to the restrictions set forth in Section 6.4 with respect to
the number of legal counsel, such Investor will promptly reimburse each Company
Indemnified Person for any legal or other expenses (promptly as such expenses
are incurred and due and payable) reasonably incurred by them in connection with
investigating or defending any such Claim. However, the indemnity agreement
contained in this Section 6.2 does not apply to amounts paid in settlement of
any Claim if such settlement is effected without the prior written consent of
such Investor, which consent will not be unreasonably withheld, and no Investor
will be liable under this Agreement (including this Section 6.2 and Article VII)
for the amount of any Claim that exceeds the net proceeds actually received by
such Investor as a result of the sale of Registrable Common Shares pursuant to
such Registration Statement. This indemnity will remain in full force and effect
regardless of any investigation made by or on behalf of a Company Indemnified
Party and will survive the transfer of the Registrable Common Shares by the
Investors under Article IX of this Agreement.

      6.3   If any proceeding shall be brought or asserted against any person
entitled to indemnity under Sections 6.1 or 6.2 hereof (an "Indemnified Party"),
such Indemnified Party promptly shall notify the person from whom indemnity is
sought (the "Indemnifying Party") in writing, and the Indemnifying Party shall
assume the defense thereof, including the employment of counsel reasonably
satisfactory to the Indemnified Party and the payment of all reasonable fees and

                                       11

<PAGE>

expenses incurred in connection with defense thereof; provided, however, that
the failure of any Indemnified Party to give such notice shall not relieve the
Indemnifying Party of its obligations or liabilities pursuant to this Agreement,
except (and only) to the extent that it shall be finally determined by a court
of competent jurisdiction (which determination is not subject to appeal or
further review) that such failure shall have proximately and materially
adversely prejudiced the Indemnifying Party.

      6.4   An Indemnified Party shall have the right to employ separate counsel
in any such proceeding and to participate in the defense thereof, but the fees
and expenses of such counsel shall be at the expense of such Indemnified Party
or Indemnified Parties unless: (i) the Indemnifying Party has agreed in writing
to pay such fees and expenses; (ii) the Indemnifying Party shall have failed
promptly to assume the defense of such proceeding and to employ counsel
reasonably satisfactory to such Indemnified Party in any such proceeding; or
(iii) the named parties to any such proceeding (including any impleaded parties)
include both such Indemnified Party and the Indemnifying Party, and such
Indemnified Party shall have been advised by counsel that a conflict of interest
is likely to exist if the same counsel were to represent such Indemnified Party
and the Indemnifying Party (in which case, if such Indemnified Party notifies
the Indemnifying Party in writing that it elects to employ separate counsel at
the expense of the Indemnifying Party, the Indemnifying Party shall not have the
right to assume the defense thereof and such counsel shall be at the reasonable
expense of the Indemnifying Party; provided, however, that in no event shall the
Indemnifying Party be responsible for the fees and expenses of more than one
separate counsel). The Indemnifying Party shall not be liable for any settlement
of any such proceeding effected without its written consent, which consent shall
not be unreasonably withheld. No Indemnifying Party shall, without the prior
written consent of the Indemnified Party, effect any settlement of any pending
proceeding in respect of which any Indemnified Party is a party, unless such
settlement includes an unconditional release of such Indemnified Party from all
liability on Claims that are the subject matter of such proceeding.

      6.5   Subject to the foregoing, all reasonable fees and expenses of the
Indemnified Party (including fees and expenses to the extent incurred in
connection with investigating or preparing to defend such proceeding in a manner
not inconsistent with this Section) shall be paid to the Indemnified Party, as
incurred, within ten (10) Business Days of written notice thereof to the
Indemnifying Party, which notice shall be delivered no more frequently than on a
monthly basis (regardless of whether it is ultimately determined that an
Indemnified Party is not entitled to indemnification hereunder; provided, that
the Indemnifying Party may require such Indemnified Party to undertake to
reimburse all such fees and expenses to the extent it is finally judicially
determined that such Indemnified Party is not entitled to indemnification
hereunder).

                                  ARTICLE VII
                                  CONTRIBUTION

      To the extent that any indemnification provided for herein is prohibited
or limited by law, the indemnifying party will make the maximum contribution
with respect to any amounts for which it would otherwise be liable under Article
VI to the fullest extent permitted by law. However, (a) no contribution will be
made under circumstances where the maker would not have been liable for
indemnification under the fault standards set forth in Article VI (without
giving effect to any prohibition or limitation or indemnification under
applicable law), (b) no person guilty of fraudulent misrepresentation (within
the meaning of Section 11(f) of the Securities Act ) will be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation,

                                       12

<PAGE>

and (c) contribution (together with any indemnification or other obligations
under this Agreement) by any seller of Registrable Common Shares will be limited
in amount to the net amount of proceeds received by such seller from the sale of
such Registrable Common Shares.

                                  ARTICLE VIII
                             EXCHANGE ACT REPORTING

      In order to make available to the Investors the benefits of Rule 144 or
any similar rule or regulation of the SEC that may at any time permit the
Investors to sell securities of the Company to the public without registration,
the Company will:

            (a)   File with the SEC in a timely manner, and make and keep
available, all reports and other documents required of the Company under the
Securities Act and the Exchange Act so long as the Company remains subject to
such requirements (it being understood that nothing herein limits the Company's
obligations under Section 4.3 of the Purchase Agreement) and file and make
available of such reports and other documents as required for the applicable
provisions of Rule 144; and

            (b)   Furnish to each Investor, so long as such Investor holds
Registrable Common Shares, promptly upon the Investor's request, (i) a written
statement by the Company that it has complied with the reporting requirements of
Rule 144, the Securities Act and the Exchange Act, (ii) a copy of the most
recent annual or quarterly report of the Company and such other reports and
documents filed by the Company with the SEC and (iii) such other information as
may be reasonably requested to permit the Investors to sell such securities
pursuant to Rule 144 without registration.

                                   ARTICLE IX
                        ASSIGNMENT OF REGISTRATION RIGHTS

      The rights of the Initial Investors hereunder, including the right to have
the Company register Registrable Common Shares pursuant to this Agreement, may
be assigned by the Initial Investors to transferees or assignees of all or any
portion of the Registrable Common Shares, but only if (a) the Investor agrees in
writing with the transferee or assignee to assign such rights, and a copy of
such agreement is furnished to the Company within a reasonable time after such
assignment, (b) the Company is, within a reasonable time after such transfer or
assignment, furnished with written notice of the name and address of such
transferee or assignee and the securities with respect to which such
registration rights are being transferred or assigned, (c) after such transfer
or assignment, the further disposition of such securities by the transferee or
assignee is restricted under the Securities Act and applicable state securities
laws, (d) at or before the time the Company received the written notice
contemplated by clause (b) of this sentence, the transferee or assignee agrees
in writing with the Company to be bound by all of the provisions contained
herein, (e) such transfer is made in accordance with the applicable requirements
of the Purchase Agreement, and (f) the transferee is an "accredited investor" as
that term is defined in Rule 501 of Regulation D.

                                   ARTICLE X
                        AMENDMENT OF REGISTRATION RIGHTS

                                       13

<PAGE>

      This Agreement may be amended and the obligations hereunder may be waived
(either generally or in a particular instance, and either retroactively or
prospectively) only with the written consent of the Company and of the Investors
who then hold a majority interest of the Registrable Common Shares. Any
amendment or waiver effected in accordance with this Article X is binding upon
each Investor and the Company.

                                   ARTICLE XI
                                  MISCELLANEOUS

      11.1  Conflicting Instructions. A person or entity is deemed to be a
holder of Registrable Common Shares whenever such person or entity owns of
record such Registrable Common Shares. If the Company receives conflicting
instructions, notices or elections from two or more persons or entities with
respect to the same Registrable Common Shares, the Company will act upon the
basis of instructions, notice or election received from the registered owner of
such Registrable Common Shares.

      11.2  Notices. Any notices required or permitted to be given under the
terms of this Agreement will be given as set forth in the Purchase Agreement.

      11.3  Waiver. Failure of any party to exercise any right or remedy under
this Agreement or otherwise, or delay by a party in exercising such right or
remedy, does not operate as a waiver thereof.

      11.4  Governing Law. This Agreement will be governed by and interpreted in
accordance with the laws of the State of Delaware without regard to the
principles of conflict of laws. The parties hereto hereby submit to the
exclusive jurisdiction of the United States federal and state courts located in
the State of Delaware with respect to any dispute arising under this Agreement,
the agreements entered into in connection herewith or the transactions
contemplated hereby or thereby. EACH PARTY HEREBY IRREVOCABLY WAIVES ANY RIGHT
THAT IT MAY HAVE TO, AND AGREES NOT TO REQUEST, A JURY TRIAL FOR THE
ADJUDICATION OF ANY DISPUTE HEREUNDER OR IN CONNECTION HEREWITH OR WITH ANY
TRANSACTION CONTEMPLATED HEREBY.

      11.5  Severability. If any provision of this Agreement is invalid or
unenforceable under any applicable statute or rule of law, then such provision
will be deemed modified in order to conform with such statute or rule of law.
Any provision hereof that may prove invalid or unenforceable under any law will
not affect the validity or enforceability of any other provision hereof.

      11.6  Entire Agreement. This Agreement and the Purchase Agreement
(including all schedules and exhibits thereto) constitute the entire agreement
among the parties hereto with respect to the subject matter hereof and thereof.
There are no restrictions, promises, warranties or undertakings, other than
those set forth or referred to herein or therein. This Agreement supersedes all
prior agreements and understandings among the parties hereto with respect to the
subject matter hereof.

      11.7  Successors and Assigns. Subject to the requirements of Article IX
hereof, this Agreement inures to the benefit of and is binding upon the
successors and assigns of each of the parties hereto. Notwithstanding anything
to the contrary herein, including, without limitation, Article

                                       14

<PAGE>

IX, the rights of an Investor hereunder are assignable to and exercisable by a
bona fide pledgee of the Registrable Common Shares in connection with an
Investor's margin or brokerage accounts.

      11.8  Headings. The headings of this Agreement are for convenience of
reference only, are not part of this Agreement and do not affect its
interpretation.

      11.9  Counterparts. This Agreement may be executed in two or more
counterparts, each of which is deemed an original but all of which constitute
one and the same agreement. This Agreement, once executed by a party, may be
delivered to the other party hereto by facsimile transmission, and facsimile
signatures are binding on the parties hereto.

      11.10 Further Assurances. Each party will do and perform, or cause to be
done and performed, all such further acts and things, and will execute and
deliver all other agreements, certificates, instruments and documents, as
another party may reasonably request in order to carry out the intent and
accomplish the purposes of this Agreement and the consummation of the
transactions contemplated hereby.

      11.11 Consents. Unless otherwise provided in this Agreement, all consents
and other determinations to be made by the Investors pursuant to this Agreement
will be made by the Investors holding a majority in interest of the Registrable
Common Shares.

      11.12 No Strict Construction. The language used in this Agreement is
deemed to be the language chosen by the parties to express their mutual intent,
and no rules of strict construction will be applied against any party.

                                       15

<PAGE>

      IN WITNESS WHEREOF, the undersigned Investors and the Company have caused
this Registration Rights Agreement to be duly executed as of the date first
above written.

                                         COMPANY:

                                         SONUS PHARMACEUTICALS, INC.

                                         By: /s/  Michael A. Martino
                                             -----------------------------------
                                         Name: Michael A. Martino
                                         Title: President & CEO

                                       16

<PAGE>

                            OMNIBUS SIGNATURE PAGE TO
                           SONUS PHARMACEUTICALS, INC.
                          REGISTRATION RIGHTS AGREEMENT

      The undersigned hereby executes and delivers the Registration Rights
Agreement to which this Signature Page is attached, which, together with all
counterparts of the Agreement and Signature Pages of the other parties named in
said Agreement, shall constitute one and the same document in accordance with
the terms of the Agreement.

                                      Entity Name: _____________________________

                                      Sign Name:   _____________________________

                                      Print Name:  _____________________________

                                      Title:       _____________________________

                                      Address:     _____________________________

                                                   _____________________________

                                                   _____________________________

                                      Telephone:   _____________________________

                                      Facsimile:   _____________________________

                                       17

<PAGE>

                                     ANNEX A

                           SONUS PHARMACEUTICALS, INC.

                 SELLING SECURITYHOLDER NOTICE AND QUESTIONNAIRE

      The undersigned beneficial owner of common stock, $.____ par value per
share (the "Common Stock"), of _________________-- (the "Company"), (the
"Registrable Securities") understands that the Company has filed or intends to
file with the Securities and Exchange Commission (the "Commission") a
registration statement on Form S-3 (the "Registration Statement") for the
registration and resale under Rule 415 of the Securities Act of 1933, as amended
(the "Securities Act"), of the Registrable Securities, in accordance with the
terms of the Registration Rights Agreement, dated as of April ___, 2004 (the
"Registration Rights Agreement"), among the Company and the Purchasers named
therein. A copy of the Registration Rights Agreement is available from the
Company upon request at the address set forth below. All capitalized terms not
otherwise defined herein shall have the meanings ascribed thereto in the
Registration Rights Agreement.

      Certain legal consequences arise from being named as a selling
securityholder in the Registration Statement and the related prospectus.
Accordingly, holders and beneficial owners of Registrable Securities are advised
to consult their own securities law counsel regarding the consequences of being
named or not being named as a selling securityholder in the Registration
Statement and the related prospectus.

                                     NOTICE

      The undersigned beneficial owner (the "Selling Securityholder") of
Registrable Securities hereby elects to include the Registrable Securities owned
by it and listed below in Item 3 (unless otherwise specified under such Item 3)
in the Registration Statement.

                                       18

<PAGE>

The undersigned hereby provides the following information to the Company and
represents and warrants that such information is accurate:

                                  QUESTIONNAIRE

1.    NAME.

      (a)   Full Legal Name of Selling Securityholder

            ____________________________________________________________________

      (b)   Full Legal Name of Registered Holder (if not the same as (a) above)
            through which Registrable Securities Listed in Item 3 below are
            held:

            ____________________________________________________________________

      (c)   Full Legal Name of Natural Control Person (which means a natural
            person who directly or indirectly alone or with others has power to
            vote or dispose of the securities covered by the questionnaire):

            ____________________________________________________________________

2.    ADDRESS FOR NOTICES TO SELLING SECURITYHOLDER:

________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Telephone: _____________________________________________________________________
Fax: ___________________________________________________________________________
Contact Person: ________________________________________________________________

3.    BENEFICIAL OWNERSHIP OF REGISTRABLE SECURITIES:

      (a)   Type and Amount of Registrable Securities beneficially owned:

            ____________________________________________________________________
            ____________________________________________________________________
            ____________________________________________________________________

                                       19

<PAGE>

4.    BROKER-DEALER STATUS:

      (a)   Are you a broker-dealer?

                               Yes [ ]     No [ ]

      Note: If yes, the Commission's staff has indicated that you should be
            identified as an underwriter in the Registration Statement.

      (b)   Are you an affiliate of a broker-dealer?

                               Yes [ ]     No [ ]

      (c)   If you are an affiliate of a broker-dealer, do you certify that you
            bought the Registrable Securities in the ordinary course of
            business, and at the time of the purchase of the Registrable
            Securities to be resold, you had no agreements or understandings,
            directly or indirectly, with any person to distribute the
            Registrable Securities?

                               Yes [ ]     No [ ]

      Note: If no, the Commission's staff has indicated that you should be
            identified as an underwriter in the Registration Statement.

5.    BENEFICIAL OWNERSHIP OF OTHER SECURITIES OF THE COMPANY OWNED BY THE
      SELLING SECURITYHOLDER.

      Except as set forth below in this Item 5, the undersigned is not the
      beneficial or registered owner of any securities of the Company other than
      the Registrable Securities listed above in Item 3.

      (a)   Type and Amount of Other Securities beneficially owned by the
            Selling Securityholder:

            ____________________________________________________________________
            ____________________________________________________________________

                                       20

<PAGE>

6.    RELATIONSHIPS WITH THE COMPANY:

      Except as set forth below, neither the undersigned nor any of its
      affiliates, officers, directors or principal equity holders (owners of 5%
      of more of the equity securities of the undersigned) has held any position
      or office or has had any other material relationship with the Company (or
      its predecessors or affiliates) during the past three years.

      State any exceptions here:

      __________________________________________________________________________
      __________________________________________________________________________

      The undersigned agrees to promptly notify the Company of any inaccuracies
or changes in the information provided herein that may occur subsequent to the
date hereof at any time while the Registration Statement remains effective.

      By signing below, the undersigned consents to the disclosure of the
information contained herein in its answers to Items 1 through 6 and the
inclusion of such information in the Registration Statement and the related
prospectus. The undersigned understands that such information will be relied
upon by the Company in connection with the preparation or amendment of the
Registration Statement and the related prospectus.

      IN WITNESS WHEREOF the undersigned, by authority duly given, has caused
this Notice and Questionnaire to be executed and delivered either in person or
by its duly authorized agent.

Dated: ________________________       Beneficial Owner: ________________________

                                      By: ______________________________________
                                          Name:
                                          Title:

PLEASE FAX A COPY OF THE COMPLETED AND EXECUTED NOTICE AND QUESTIONNAIRE, AND
RETURN THE ORIGINAL BY OVERNIGHT MAIL, TO:

                                       21