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                                                                    EXHIBIT 4.03



                               CORIXA CORPORATION

                          REGISTRATION RIGHTS AGREEMENT


        This Registration Rights Agreement (the "Agreement") is made as of the
8th day of April, 1999, by and between Corixa Corporation, a Delaware
corporation (the "Company") and Castle Gate, L.L.C., a Washington limited
liability company (the "Investor").

                                    RECITALS

        The Company and the Investor have entered into the Equity Line of Credit
and Securities Purchase Agreement (the "Purchase Agreement") of even date
herewith pursuant to which the Investor will provide to the Company a two-year
line of credit in the aggregate amount of $50,000,000 ("Credit Line") in
exchange for which the Company will issue and sell to the Investor up to 50,000
shares of Series A convertible preferred stock of the Company ("Preferred
Stock") and certain warrants to purchase shares of Common Stock of the Company
("Warrants") on the terms and conditions set forth in the Purchase Agreement. A
condition to the Investor's obligations under the Purchase Agreement is that the
Company and the Investor enter into this Agreement in order to provide the
Investor with certain rights to register shares of the Company's Common Stock
issuable upon conversion of the Preferred Stock held by the Investor and to
provide the Company with certain rights to notices of sales by Investor each as
set forth herein, upon the terms and conditions set forth herein.

                                    AGREEMENT

        The parties hereby agree as follows:

        1.     REGISTRATION RIGHTS.  The Company and the Investor covenant and
agree as follows:

               1.1 DEFINITIONS. For purposes of this Section 1:

                      (a) The terms "register," "registered," and "registration"
refer to a registration effected by preparing and filing a registration
statement or similar document in compliance with the Securities Act of 1933, as
amended (the "Securities Act"), and the declaration or ordering of effectiveness
of such registration statement or document;

                      (b) The term "Registrable Securities" means (i) the shares
of Common Stock issuable or issued upon conversion of the Preferred Stock, (ii)
the shares of Common Stock issuable or issued upon exercise of the Warrants, and
(iii) any other shares of Common Stock of the Company issued as (or issuable
upon the conversion or exercise of any warrant, right or other security which is
issued as) a dividend or other distribution with respect to, or in exchange for
or in replacement of, the shares listed in (i) or (ii); provided, however, that
the foregoing definition shall exclude in all cases any Registrable Securities
sold by a person in a transaction in which his or her rights under this
Agreement are not assigned. Notwithstanding


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the foregoing, Common Stock or other securities shall only be treated as
Registrable Securities if and so long as they have not been (A) sold to or
through a broker or dealer or underwriter in a public distribution or a public
securities transaction, or (B) sold in a transaction exempt from the
registration and prospectus delivery requirements of the Securities Act under
Section 4(1) thereof so that all transfer restrictions, and restrictive legends
with respect thereto, if any, are removed upon the consummation of such sale;

                      (c) The number of shares of "Registrable Securities then
outstanding" shall be determined by the number of shares of Common Stock
outstanding which are, and the number of shares of Common Stock issuable
pursuant to then exercisable or convertible securities which are, Registrable
Securities;

                      (d) The term "Holder" means any person owning or having
the right to acquire Registrable Securities or any assignee thereof in
accordance with Section 1.9 of this Agreement;

                      (e) The term "Form S-3" means such form under the
Securities Act as in effect on the date hereof or any successor form that
permits significant incorporation by reference of the Company's filings under
the Securities Exchange Act of 1934, as amended (the "Exchange Act"); and

                      (f) The term "SEC" means the Securities and Exchange
Commission.

               1.2 FORM S-3 REGISTRATION. Unless otherwise instructed in writing
by the Holder, within thirty (30) days after any conversion of shares of
Preferred Stock held by Holder into shares of Common Stock in accordance with
Section 6 of the Certificate of Designation (as defined in the Purchase
Agreement), the Company will use its best efforts to effect a registration on
Form S-3 and all related qualifications and compliances as would permit or
facilitate the sale and distribution of such shares of Holder's Registrable
Securities that Holder requests; provided, however, that the Company shall not
be obligated to effect any such registration, qualification or compliance
pursuant to this Section 1.2: (a) if Form S-3 is not available for such offering
by the Holder; (b) if the Holder proposes to sell Registrable Securities having
an aggregate value of less than $10,000,000 based upon the applicable conversion
or exercise price for such shares of Registrable Securities, respectively, as
determined in accordance with Section 6(C) of the Certificate of Designation or
the applicable Warrants, respectively; (c) if the Company shall furnish to the
Holder a certificate signed by the President of the Company stating that in the
good faith judgment of the Board of Directors of the Company, it would be
seriously detrimental to the Company and its stockholders for such Form S-3
Registration to be effected at such time, in which event the Company shall have
the right to defer the filing of the Form S-3 registration statement for a
period of not more than 120 days after the applicable conversion of Holder's
Preferred Stock to Common Stock; provided, however, that the Company shall not
utilize this right more than once in any twelve-month period; (d) in any
particular jurisdiction in which the Company would be required to qualify to do
business or to execute a general consent to service of process in effecting such
registration, qualification or compliance; or (e) during the period ending
ninety (90) days after the effective date of a registration statement pursuant
to which the


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Company registered any of its stock under the Securities Act in connection with
the public offering of such securities solely for cash.

               1.3 OBLIGATIONS OF THE COMPANY. Whenever required under Section
1.2 to effect the registration of any Registrable Securities, the Company shall,
as expeditiously as reasonably possible, use its best commercial efforts to:

                      (a) Prepare and file with the SEC a registration statement
with respect to such Registrable Securities and cause such registration
statement to become effective, and, upon the request of the Holder of the
Registrable Securities registered thereunder, keep such registration statement
effective for up to one hundred twenty (120) days. The Company shall not be
required to file, cause to become effective or maintain the effectiveness of any
registration statement that contemplates a distribution of securities on a
delayed or continuous basis pursuant to Rule 415 under the Securities Act.

                      (b) Prepare and file with the SEC such amendments and
supplements to such registration statement and the prospectus used in connection
with such registration statement as may be necessary to comply with the
provisions of the Securities Act with respect to the disposition of all
Registrable Securities covered by such registration statement for up to one
hundred twenty (120) days.

                      (c) Furnish to the Holder such numbers of copies of a
prospectus, including a preliminary prospectus, in conformity with the
requirements of the Securities Act, and such other documents as the Holder may
reasonably request in order to facilitate the disposition of Registrable
Securities owned by the Holder.

                      (d) Register and qualify the Registrable Securities
covered by such registration statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably requested by the Holder,
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions.

                      (e) Notify the Holder of Registrable Securities covered by
such registration statement at any time when a prospectus relating thereto is
required to be delivered under the Securities Act of the happening of any event
as a result of which the prospectus included in such 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 not misleading in the light of the circumstances then
existing, such obligation to continue for one hundred twenty (120) days.

                      (f) Cause all such Registrable Securities registered
pursuant the Section 1.2 to be listed on each securities exchange on which
similar securities issued by the Company are then listed.



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                      (g) Provide a transfer agent and registrar for all
Registrable Securities registered pursuant hereunder and a CUSIP number for all
such Registrable Securities, in each case not later than the effective date of
such registration.

                      (h) Furnish, at the request of the Holder, on the date
that the registration statement with respect to such securities becomes
effective, (i) an opinion, dated such date, of the counsel representing the
Company for the purposes of such registration, in form and substance as is
customarily given to underwriters in an underwritten public offering, addressed
to the Holder and (ii) a letter dated such date, from the independent certified
public accountants of the Company, in form and substance as is customarily given
by independent certified public accountants to underwriters in an underwritten
public offering, addressed to the Holder.

               1.4 RESTRICTIONS ON AND PROCEDURE FOR SALES PURSUANT TO A
REGISTRATION STATEMENT.

                      (a)    Each Holder agrees to the following:

                             (i) Notice to Company. If Holder shall propose to
sell any Registrable Securities that have been registered in accordance with
this Section 1, the Holder shall notify the Company of its intent to do so on or
before three (3) business days prior to the date of such sale (the "Notice of
Sale"), and the provision of the Notice of Sale to the Company shall
conclusively be deemed to establish an agreement by the Holder to comply with
the registration provisions herein described. The Notice of Sale shall be deemed
to constitute a representation that any information supplied by the Holder in
connection with the Notice of Sale is accurate as of the date of such Notice of
Sale.

                             (ii) Notice of Sale. The Notice of Sale in
substantially the form attached as Attachment A shall be given in accordance
with the provisions of Section 2.3 hereof. However, the Holder may give the
Notice of Sale orally by telephoning the Chief Financial Officer at the Company
at (206) 754-5711. An oral Notice of Sale shall be deemed to have been received
only at such time as the Holder speaks directly with the Chief Financial
Officer. In addition, an oral Notice of Sale shall only be deemed effective if
it is followed by a written Notice of Sale received by the Company by personal
delivery or facsimile within twenty-four (24) hours after giving the oral Notice
of Sale.

                             (iii) Delay of Sale. The Company may refuse to
permit the Holder to resell any Registrable Securities for a specified period of
time; provided, however, that (a) in order to exercise this right, the Company
must deliver a certificate in writing to the Holder to the effect that the
registration statement in its then current form contains an untrue statement of
material fact or omits to state a material fact necessary in order to make the
statements made therein, in light of the circumstances under which they were
made, not misleading, and (b) in no event shall such delay exceed twenty-five
(25) days, and (c) in no event shall this right of delay be exercised on more
than one (1) occasion in any twelve (12) month period. During any suspension as
contemplated by this Section 1.4 (a)(iii), the Company will not allow any of its
officers or directors to buy or sell shares of the Company's securities.



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               1.5 FURNISH INFORMATION. It shall be a condition precedent to the
obligations of the Company to take any action pursuant to this Section 1 with
respect to the Registrable Securities of the Holder that the Holder shall
furnish to the Company such information regarding itself, the Registrable
Securities held by it, and the intended method of disposition of such securities
as shall be required to effect the registration of such Holder's Registrable
Securities. The Company shall have no obligation with respect to any
registration requested pursuant to Section 1.2 of this Agreement if, as a result
of the application of the preceding sentence, the anticipated aggregate value of
the Registrable Securities to be included in the registration does not equal or
exceed the anticipated aggregate value required to originally trigger the
Company's obligation to initiate such registration as specified in subsection
1.2(b).

               1.6 EXPENSES OF REGISTRATION ON FORM S-3. All expenses incurred
in connection with a registration requested pursuant to Section 1.2, including
(without limitation) all registration, filing, qualification, printers' and
accounting fees and the reasonable fees and disbursements of one counsel for the
selling Holder selected by Holder with the approval of the Company, which
approval shall not be unreasonably withheld, and counsel for the Company shall
be borne by the Company.

               1.7 INDEMNIFICATION. In the event any Registrable Securities are
included in a registration statement under Section 1:

                      (a) To the extent permitted by law, the Company will
indemnify and hold harmless Holder and each person, if any, who controls Holder
or underwriter within the meaning of the Securities Act or the Exchange Act,
against any losses, claims, damages, or liabilities (joint or several) to which
they may become subject under the Securities Act, the Exchange Act or other
federal or state law, insofar as such losses, claims, damages, or liabilities
(or actions in respect thereof) arise out of or are based upon any of the
following statements, omissions or violations (collectively a "Violation"): (i)
any untrue statement or alleged untrue statement of a material fact contained in
such registration statement, including any preliminary prospectus or final
prospectus contained therein or any amendments or supplements thereto, (ii) 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, or
(iii) any violation or alleged violation by the Company of the Securities Act,
the Exchange Act, any state securities law or any rule or regulation promulgated
under the Securities Act, the Exchange Act or any state securities law; and the
Company will pay to each such Holder or controlling person, as incurred, any
legal or other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, damage, liability, or action;
provided, however, that the indemnity agreement contained in this subsection
1.7(a) shall not apply to amounts paid in settlement of any such loss, claim,
damage, liability, or action if such settlement is effected without the consent
of the Company (which consent shall not be unreasonably withheld), nor shall the
Company be liable to any Holder or controlling person for any such loss, claim,
damage, liability, or action to the extent that it arises out of or is based
upon a Violation which occurs in reliance upon and in conformity with written
information furnished expressly for use in connection with such registration by
any such Holder or controlling person.



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                      (b) To the extent permitted by law, the Holder will
indemnify and hold harmless the Company, each of its directors, each of its
officers who has signed the registration statement, each person, if any, who
controls the Company within the meaning of the Securities Act and any
controlling person of any Holder, against any losses, claims, damages, or
liabilities (joint or several) to which any of the foregoing persons may become
subject, under the Securities Act, the Exchange Act or other federal or state
law, insofar as such losses, claims, damages, or liabilities (or actions in
respect thereto) arise out of or are 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 by Holder expressly for use
in connection with such registration; and Holder will pay, as incurred, any
legal or other expenses reasonably incurred by any person intended to be
indemnified pursuant to this subsection 1.7(b), in connection with investigating
or defending any such loss, claim, damage, liability, or action; provided,
however, that the indemnity agreement contained in this subsection 1.7(b) shall
not apply to amounts paid in settlement of any such loss, claim, damage,
liability or action if such settlement is effected without the consent of the
Holder, which consent shall not be unreasonably withheld; provided, that in no
event shall any indemnity under this subsection 1.7(b) exceed the net proceeds
from the offering received by Holder, except in the case of willful fraud by
Holder.

                      (c) Promptly after receipt by an indemnified party under
this Section 1.7 of notice of the commencement of any action (including any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying party under this Section 1.7, deliver to
the indemnifying party a written notice of the commencement thereof and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume the defense thereof with counsel mutually
satisfactory to the parties; provided, however, that an indemnified party
(together with all other indemnified parties which may be represented without
conflict by one counsel) shall have the right to retain one separate counsel,
with the reasonable fees and expenses to be paid by the indemnifying party, if
representation of such indemnified party by the counsel retained by the
indemnifying party would be inappropriate due to actual or potential differing
interests between such indemnified party and any other party represented by such
counsel in such proceeding. The failure to deliver written notice to the
indemnifying party within a reasonable time of the commencement of any such
action, if prejudicial to its ability to defend such action, shall relieve such
indemnifying party of any liability to the indemnified party under this Section
1.7 but the omission so to deliver written notice to the indemnifying party will
not relieve it of any liability that it may have to any indemnified party
otherwise than under this Section 1.7.

                      (d) If the indemnification provided for in this Section
1.7 is held by a court of competent jurisdiction to be unavailable to an
indemnified party with respect to any loss, liability, claim, damage or expense
referred to therein, then the indemnifying party, in lieu of indemnifying such
indemnified party hereunder, shall contribute to the amount paid or payable by
such indemnified party as a result of such loss, liability, claim, damage, or
expense in such proportion as is appropriate to reflect the relative fault of
the indemnifying party on the one hand and of the indemnified party on the other
in connection with the statements or omissions that resulted in such loss,
liability, claim, damage or expense as well as any other relevant equitable



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considerations; provided, that in no event shall any contribution by Holder
under this subsection 1.7(d) exceed the net proceeds from the offering received
by Holder, except in the case of willful fraud by Holder. The relative fault of
the indemnifying party and of the indemnified party shall be determined by
reference to, among other things, whether the untrue or alleged untrue statement
of a material fact or the omission to state a material fact relates to
information supplied by the indemnifying party or by the indemnified party and
the parties' relative intent, knowledge, access to information, and opportunity
to correct or prevent such statement or omission.

                      (e) The obligations of the Company and Holder under this
Section 1.7 shall survive the completion of any offering of Registrable
Securities in a registration statement under this Section 1, and otherwise.

               1.8 REPORTS UNDER SECURITIES EXCHANGE ACT OF 1934. With a view to
making available to the Holder the benefits of Rule 144 promulgated under the
Securities Act and any other rule or regulation of the SEC that may at any time
permit a Holder to sell securities of the Company to the public without
registration or pursuant to a registration on Form S-3, the Company agrees to
use its best commercial efforts to:

                      (a) make and keep public information available, as those
terms are understood and defined in SEC Rule 144, at all times so long as the
Company remains subject to the periodic reporting requirements under Sections 13
or 15(d) of the Exchange Act;

                      (b) take such action, including the voluntary registration
of its Common Stock under Section 12 of the Exchange Act, as is necessary to
enable the Holder to utilize Form S-3 for the sale of its Registrable
Securities;

                      (c) file with the SEC in a timely manner all reports and
other documents required of the Company under the Securities Act and the
Exchange Act; and

                      (d) furnish to Holder, so long as Holder owns any
Registrable Securities, forthwith upon request (i) a written statement by the
Company that it has complied with the reporting requirements of SEC Rule 144,
the Securities Act and the Exchange Act, or that it qualifies as a registrant
whose securities may be resold pursuant to Form S-3 (at any time when it so
qualifies), (ii) a copy of the most recent annual or quarterly report of the
Company and such other reports and documents so filed by the Company, and (iii)
such other information as may be reasonably requested in availing any Holder of
any rule or regulation of the SEC which permits the selling of any such
securities without registration or pursuant to such form.

               1.9 ASSIGNMENT OF REGISTRATION RIGHTS. The right to cause the
Company to register Registrable Securities pursuant to Section 1.2 may not be
assigned without the Company's prior written consent; provided, however, such
consent shall not be required in connection with the assignment by the Investor
of such registration rights (but only with all related obligations) to (i) an
Affiliate of the Investor (as such term is defined in the Standstill Agreement),
(ii) an entity solely in connection with charitable contributions by the
Investor or (iii) an individual or entity solely for estate planning purposes,
provided that (x) written notice is provided to the Company five (5) business
days prior to any such assignment, (y) a minimum of



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5,000 shares of Registrable Securities are assigned in each instance, and (z)
immediately following such assignment the further disposition of such securities
by the transferee or assignee is restricted under the Securities Act and the
transferee or assignee agrees in writing to be bound by all of the provisions of
this Agreement.

               1.10 "MARKET STAND-OFF" AGREEMENT. Holder hereby agrees that,
during the period of duration (up to, but not exceeding, 90 days) specified by
the Company and an underwriter of Common Stock or other securities of the
Company, following the effective date of a registration statement of the Company
filed under the Securities Act, it shall not, to the extent requested by the
Company and such underwriter, directly or indirectly sell, offer to sell,
contract to sell (including, without limitation, any short sale), grant any
option to purchase or otherwise transfer or dispose of (other than to donees who
agree to be similarly bound) any securities of the Company held by it at any
time during such period except Common Stock included in such registration.

               In order to enforce the foregoing covenant, the Company may
impose stop-transfer instructions with respect to the Registrable Securities of
the Holder (and the shares or securities of every other person subject to the
foregoing restriction) until the end of such period, and the Holder agrees that,
if so requested, the Holder will execute an agreement in the form provided by
the underwriter containing terms which are essentially consistent with the
provisions of this Section 1.10.

               1.11 TERMINATION OF REGISTRATION RIGHTS. With respect to shares
of Registrable Securities issued to the Investor at the Initial Closing or any
particular Subsequent Closing(s) (as such terms are defined in the Purchase
Agreement), the Holder shall not be entitled to exercise any right provided for
in this Section 1 after such time as Rule 144(k) or another similar exemption
under the Securities Act is available for the sale of all of such Holder's
shares that were issued at the Initial Closing or the applicable Subsequent
Closing, respectively, during a three (3) month period without registration. For
purposes of clarity, the registration rights of a Holder provided for in this
Section 1 shall terminate in stages, which stages shall correspond to the
initial issuance date of such Registrable Securities.

        2.     MISCELLANEOUS.

               2.1 SUCCESSORS AND ASSIGNS. Except as otherwise provided in this
Agreement, the terms and conditions of this Agreement shall inure to the benefit
of and be binding upon the respective permitted successors and assigns of the
parties (including transferees of any of the Preferred Stock or any Common Stock
issued upon conversion thereof). Nothing in this Agreement, express or implied,
is intended to confer upon any party other than the parties hereto or their
respective successors and assigns any rights, remedies, obligations, or
liabilities under or by reason of this Agreement, except as expressly provided
in this Agreement.

               2.2 AMENDMENTS AND WAIVERS. Any term of this Agreement may be
amended or waived only with the written consent of the Company and the holders
of a majority of the Registrable Securities then outstanding. Any amendment or
waiver effected in accordance



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with this paragraph shall be binding upon each holder of any Registrable
Securities then outstanding, each future holder of all such Registrable
Securities, and the Company.

               2.3 NOTICES. Unless otherwise provided, any notice required or
permitted by this Agreement shall be in writing and shall be deemed sufficient
upon delivery, when delivered personally or by overnight courier or sent by
telegram or fax, or forty-eight (48) hours after being deposited in the U.S.
mail, as certified or registered mail, with postage prepaid, and addressed to
the party to be notified at such party's address or fax number as set forth on
the signature page hereto or as subsequently modified by written notice, and if
to Investor, with a copy to Mark Beatty, Preston Gates & Ellis, 701 Fifth
Avenue, #5000, Seattle, Washington 98104, and if to Corixa, with a copy to
William W. Ericson, Venture Law Group, 4750 Carillon Point, Kirkland, Washington
98033.

               2.4 SEVERABILITY. If one or more provisions of this Agreement are
held to be unenforceable under applicable law, the parties agree to renegotiate
such provision in good faith. In the event that the parties cannot reach a
mutually agreeable and enforceable replacement for such provision, then (a) such
provision shall be excluded from this Agreement, (b) the balance of the
Agreement shall be interpreted as if such provision were so excluded and (c) the
balance of the Agreement shall be enforceable in accordance with its terms.

               2.5 GOVERNING LAW. This Agreement and all acts and transactions
pursuant hereto shall be governed, construed and interpreted in accordance with
the laws of the State of Washington, without giving effect to principles of
conflicts of laws.

               2.6 COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

               2.7 TITLES AND SUBTITLES. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.




                            [Signature Page Follows]



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        The parties have executed this Registration Rights Agreement as of the
date first above written.

                                        COMPANY:


                                        CORIXA CORPORATION

                                        By:  /s/ Steven Gillis
                                           -------------------------------------
                                           Steven Gillis
                                           Chairman and Chief Executive Officer

                                        Address: 1124 Columbia Street, Suite 200
                                                 Seattle, Washington 98104

                                        Fax:  (206) 754-5762


                                        INVESTOR:


                                        CASTLE GATE, L.L.C.

                                        By: /s/ Michael Larson
                                           -------------------------------------

                                        Name: Michael Larson
                                             -----------------------------------
                                                          (print)

                                        Title: Business Manager
                                              ----------------------------------



                              SIGNATURE PAGE TO THE
                          REGISTRATION RIGHTS AGREEMENT

<PAGE>   11

                                  ATTACHMENT A

                               CORIXA CORPORATION

                                 NOTICE OF SALE



        Pursuant to the Registration Rights Agreement dated as of April 8, 1999
by and between Corixa Corporation (the "Company") and Castle Gate, L.L.C., a
Washington limited liability company, the undersigned hereby gives notice to the
Company of the undersigned's intent to sell _______ shares of the Company's
Common Stock registered pursuant to the registration statement on ___________
(File No. ______ ).



Dated:                                  By:
       --------------  ------              -------------------------------------
                                                      (signature)


                                        Name:
                                             -----------------------------------
                                                         (print)


                                        Title:
                                              ----------------------------------
                                                      (if applicable)