<PAGE>

                                                                    Exhibit 10.6

                                 XENOPORT, INC.

                                 1999 STOCK PLAN

                             STOCK OPTION AGREEMENT

      Unless otherwise defined herein, the terms defined in the 1999 Stock Plan
shall have the same defined meanings in this Stock Option Agreement.

      I.    NOTICE OF STOCK OPTION GRANT

      [OPTIONEE'S NAME AND ADDRESS]

      The undersigned Optionee has been granted an Option to purchase Common
Stock of the Company, subject to the terms and conditions of the Plan and this
Option Agreement, as follows:

      Grant Number                      ___________________________

      Date of Grant                     ___________________________

      Vesting Commencement Date         ___________________________

      Exercise Price per Share          $__________________________

      Total Number of Shares Granted    ___________________________

      Total Exercise Price              $__________________________

      Type of Option:                   ___ Incentive Stock Option

                                        ___ Nonstatutory Stock Option

      Term/Expiration Date:             ___________________________

      Vesting Schedule:

      This Option shall be exercisable, in whole or in part, according to the
following vesting schedule:

      [25% of the Shares subject to the Option shall vest twelve months after
the Vesting Commencement Date, and 1/48 of the Shares subject to the Option
shall vest each month thereafter, subject to Optionee's continuing to be a
Service Provider on such dates.]

<PAGE>

      Termination Period:

      This Option shall be exercisable for three months after Optionee ceases to
be a Service Provider. Upon Optionee's death or Disability, this Option may be
exercised for one year after Optionee ceases to be a Service Provider. In no
event may Optionee exercise this Option after the Term/Expiration Date as
provided above.

      II.   AGREEMENT

            1. Grant of Option. The Plan Administrator of the Company hereby
grants to the Optionee named in the Notice of Grant (the "Optionee"), an option
(the "Option") to purchase the number of Shares set forth in the Notice of
Grant, at the exercise price per Share set forth in the Notice of Grant (the
"Exercise Price"), and subject to the terms and conditions of the Plan, which is
incorporated herein by reference. Subject to Section 14(c) of the Plan, in the
event of a conflict between the terms and conditions of the Plan and this Option
Agreement, the terms and conditions of the Plan shall prevail.

      If designated in the Notice of Grant as an Incentive Stock Option ("ISO"),
this Option is intended to qualify as an Incentive Stock Option as defined in
Section 422 of the Code. Nevertheless, to the extent that it exceeds the
$100,000 rule of Code Section 422(d), this Option shall be treated as a
Nonstatutory Stock Option ("NSO").

            2. Exercise of Option.

                  (a) Right to Exercise. This Option shall be exercisable during
its term in accordance with the Vesting Schedule set out in the Notice of Grant
and with the applicable provisions of the Plan and this Option Agreement.

                  (b) Method of Exercise. This Option shall be exercisable by
delivery of an exercise notice in the form attached as Exhibit A (the "Exercise
Notice") which shall state the election to exercise the Option, the number of
Shares with respect to which the Option is being exercised, and such other
representations and agreements as may be required by the Company. The Exercise
Notice shall be accompanied by payment of the aggregate Exercise Price as to all
Exercised Shares. This Option shall be deemed to be exercised upon receipt by
the Company of such fully executed Exercise Notice accompanied by the aggregate
Exercise Price.

      No Shares shall be issued pursuant to the exercise of an Option unless
such issuance and such exercise complies with Applicable Laws. Assuming such
compliance, for income tax purposes the Shares shall be considered transferred
to the Optionee on the date on which the Option is exercised with respect to
such Shares.

            3. Optionee's Representations. In the event the Shares have not been
registered under the Securities Act of 1933, as amended, at the time this Option
is exercised, the Optionee shall, if required by the Company, concurrently with
the exercise of all or any portion of this Option, deliver to the Company his or
her Investment Representation Statement in the form attached hereto as Exhibit B

                                      -2-
<PAGE>

and shall read the applicable rules of the Commissioner of Corporations attached
to such Investment Representation Statement.

            4. Lock-Up Period. Optionee hereby agrees that, if so requested by
the Company or any representative of the under-writers (the "Managing
Underwriter") in connection with any registration of the offering of any
securities of the Company under the Securities Act, Optionee shall not sell or
otherwise transfer any Shares or other securities of the Company during the
180-day period (or such other period as may be requested in writing by the
Managing Underwriter and agreed to in writing by the Company) (the "Market
Standoff Period") following the effective date of a registration statement of
the Company filed under the Securities Act. Such restriction shall apply only to
the first registration statement of the Company to become effective under the
Securities Act that includes securities to be sold on behalf of the Company to
the public in an underwritten public offering under the Securities Act. The
Company may impose stop-transfer instructions with respect to securities subject
to the foregoing restrictions until the end of such Market Standoff Period.

            5. Method of Payment. Payment of the aggregate Exercise Price shall
be by any of the following, or a combination thereof, at the election of the
Optionee:

                  (a) cash or check;

                  (b) consideration received by the Company under a formal
cashless exercise program adopted by the Company in connection with the Plan; or

                  (c) surrender of other Shares which, (i) in the case of Shares
acquired upon exercise of an option, have been owned by the Optionee for more
than six (6) months on the date of surrender, and (ii) have a Fair Market Value
on the date of surrender equal to the aggregate Exercise Price of the Exercised
Shares.

            6. Restrictions on Exercise. This Option may not be exercised until
such time as the Plan has been approved by the shareholders of the Company, or
if the issuance of such Shares upon such exercise or the method of payment of
consideration for such shares would constitute a violation of any Applicable
Law.

            7. Non-Transferability of Option. This Option may not be transferred
in any manner otherwise than by will or by the laws of descent or distribution
and may be exercised during the lifetime of Optionee only by Optionee. The terms
of the Plan and this Option Agreement shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

            8. Term of Option. This Option may be exercised only within the term
set out in the Notice of Grant, and may be exercised during such term only in
accordance with the Plan and the terms of this Option.

            9. Tax Consequences. Set forth below is a brief summary as of the
date of this Option of some of the federal tax consequences of exercise of this
Option and disposition of the Shares. THIS SUMMARY IS NECESSARILY INCOMPLETE,
AND THE TAX LAWS AND

                                      -3-
<PAGE>

REGULATIONS ARE SUBJECT TO CHANGE. THE OPTIONEE SHOULD CONSULT A TAX ADVISER
BEFORE EXERCISING THIS OPTION OR DISPOSING OF THE SHARES.

                  (a) Exercise of NSO. There may be a regular federal income tax
liability upon the exercise of an NSO. The Optionee will be treated as having
received compensation income (taxable at ordinary income tax rates) equal to the
excess, if any, of the Fair Market Value of the Shares on the date of exercise
over the Exercise Price. If Optionee is an Employee or a former Employee, the
Company will be required to withhold from Optionee's compensation or collect
from Optionee and pay to the applicable taxing authorities an amount in cash
equal to a percentage of this compensation income at the time of exercise, and
may refuse to honor the exercise and refuse to deliver Shares if such
withholding amounts are not delivered at the time of exercise.

                  (b) Exercise of ISO. If this Option qualifies as an ISO, there
will be no regular federal income tax liability upon the exercise of the Option,
although the excess, if any, of the Fair Market Value of the Shares on the date
of exercise over the Exercise Price will be treated as an adjustment to the
alternative minimum tax for federal tax purposes and may subject the Optionee to
the alternative minimum tax in the year of exercise.

                  (c) Disposition of Shares. In the case of an NSO, if Shares
are held for at least one year, any gain realized on disposition of the Shares
will be treated as long-term capital gain for federal income tax purposes. In
the case of an ISO, if Shares transferred pursuant to the Option are held for at
least one year after exercise and of at least two years after the Date of Grant,
any gain realized on disposition of the Shares will also be treated as long-term
capital gain for federal income tax purposes. If Shares purchased under an ISO
are disposed of within one year after exercise or two years after the Date of
Grant, any gain realized on such disposition will be treated as compensation
income (taxable at ordinary income rates) to the extent of the difference
between the Exercise Price and the lesser of (1) the Fair Market Value of the
Shares on the date of exercise, or (2) the sale price of the Shares. Any
additional gain will be taxed as capital gain, short-term or long-term depending
on the period that the ISO Shares were held.

                  (d) Notice of Disqualifying Disposition of ISO Shares. If the
Option granted to Optionee herein is an ISO, and if Optionee sells or otherwise
disposes of any of the Shares acquired pursuant to the ISO on or before the
later of (1) the date two years after the Date of Grant, or (2) the date one
year after the date of exercise, the Optionee shall immediately notify the
Company in writing of such disposition. Optionee agrees that Optionee may be
subject to income tax withholding by the Company on the compensation income
recognized by the Optionee.

            10. Entire Agreement; Governing Law. The Plan is incorporated herein
by reference. The Plan and this Option Agreement constitute the entire agreement
of the parties with respect to the subject matter hereof and supersede in their
entirety all prior undertakings and agreements of the Company and Optionee with
respect to the subject matter hereof, and may not be modified adversely to the
Optionee's interest except by means of a writing signed by the Company and
Optionee. This agreement is governed by the internal substantive laws but not
the choice of law rules of California.

                                      -4-
<PAGE>

            11. No Guarantee of Continued Service. OPTIONEE ACKNOWLEDGES AND
AGREES THAT THE VESTING OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS
EARNED ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (NOT
THROUGH THE ACT OF BEING HIRED, BEING GRANTED THIS OPTION OR ACQUIRING SHARES
HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES THAT THIS AGREEMENT, THE
TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING SCHEDULE SET FORTH HEREIN DO
NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS A
SERVICE PROVIDER FOR THE VESTING PERIOD, FOR ANY PERIOD, OR AT ALL, AND SHALL
NOT INTERFERE IN ANY WAY WITH OPTIONEE'S RIGHT OR THE COMPANY'S RIGHT TO
TERMINATE OPTIONEE'S RELATIONSHIP AS A SERVICE PROVIDER AT ANY TIME, WITH OR
WITHOUT CAUSE.

      Optionee acknowledges receipt of a copy of the Plan and represents that he
or she is familiar with the terms and provisions thereof, and hereby accepts
this Option subject to all of the terms and provisions thereof. Optionee has
reviewed the Plan and this Option in their entirety, has had an opportunity to
obtain the advice of counsel prior to executing this Option and fully
understands all provisions of the Option. Optionee hereby agrees to accept as
binding, conclusive and final all decisions or interpretations of the
Administrator upon any questions arising under the Plan or this Option. Optionee
further agrees to notify the Company upon any change in the residence address
indicated below.

OPTIONEE                                            XENOPORT, MC.

____________________________                        ____________________________
Signature                                           By

____________________________                        ____________________________
Print Name                                          Its

Address of Residence:                               Address:

____________________________                        ____________________________
____________________________                        ____________________________
____________________________                        ____________________________

                                                    ____________________________
                                                    Date Received

                                      -5-
<PAGE>

                                                                    Exhibit 10.6

                                    EXHIBIT A

                                 XENOPORT, INC.
                                 1999 STOCK PLAN
                                 EXERCISE NOTICE

XenoPort, Inc.
2631 Hanover Street
Palo Alto, CA 94304

Attention: Chief Executive Officer

      1. Exercise of Option. Effective as of today, _____________, ____, the
undersigned ("Optionee") hereby elects to exercise Optionee's option to purchase
_________ shares of the Common Stock (the "Shares") of XenoPort, Inc. (the
"Company") under and pursuant to the 1999 Stock Plan (the "Plan") and the Stock
Option Agreement dated ____________, ________ (the "Option Agreement").

      2. Delivery of Payment. Purchaser herewith delivers to the Company the
full purchase price of the Shares, as set forth in the Option Agreement.

      3. Representations of Optionee. Optionee acknowledges that Optionee has
received, read and understood the Plan and the Option Agreement and agrees to
abide by and be bound by their terms and conditions.

      4. Rights as Shareholder. Until the issuance of the Shares (as evidenced
by the appropriate entry on the books of the Company or of a duly authorized
transfer agent of the Company), no right to vote or receive dividends or any
other rights as a shareholder shall exist with respect to the Optioned Stock,
notwithstanding the exercise of the Option. The Shares shall be issued to the
Optionee as soon as practicable after the Option is exercised. No adjustment
shall be made for a dividend or other right for which the record date is prior
to the date of issuance except as provided in Section 12 of the Plan.

      5. Company's Right of First Refusal. Before any Shares held by Optionee or
any transferee (either being sometimes referred to herein as the "Holder") may
be sold or otherwise transferred (including transfer by gift or operation of
law), the Company or its assignee(s) shall have a right of first refusal to
purchase the Shares on the terms and conditions set forth in this Section (the
"Right of First Refusal").

            (a) Notice of Proposed Transfer. The Holder of the Shares shall
deliver to the Company a written notice (the "Notice") stating: (i) the Holder's
bona fide intention to sell or otherwise transfer such Shares; (ii) the name of
each proposed purchaser or other transferee ("Proposed Transferee"); (iii) the
number of Shares to be transferred to each Proposed Transferee; and (iv) the
bona fide cash price or other consideration for which the Holder pro-poses to
transfer the Shares (the "Offered Price"), and the Holder shall offer the Shares
at the Offered Price to the Company or its assignee(s).

<PAGE>

            (b) Exercise of Right of First Refusal. At any time within thirty
(30) days after receipt of the Notice, the Company and/or its assignee(s) may,
by giving written notice to the Holder, elect to purchase all, but not less than
all, of the Shares proposed to be transferred to any one or more of the Proposed
Transferees, at the purchase price determined in accordance with subsection (c)
below.

            (c) Purchase Price. The purchase price ("Purchase Price") for the
Shares purchased by the Company or its assignee(s) under this Section shall be
the Offered Price. If the Offered Price includes consideration other than cash,
the cash equivalent value of the non-cash consideration shall be determined by
the Board of Directors of the Company in good faith.

            (d) Payment. Payment of the Purchase Price shall be made, at the
option of the Company or its assignee(s), in cash (by check), by cancellation of
all or a portion of any outstanding indebtedness of the Holder to the Company
(or, in the case of repurchase by an assignee, to the assignee), or by any
combination thereof within 30 days after receipt of the Notice or in the manner
and at the times set forth in the Notice.

            (e) Holder's Right to Transfer. If all of the Shares proposed in the
Notice to be transferred to a given Proposed Transferee are not purchased by the
Company and/or its assignee(s) as provided in this Section, then the Holder may
sell or otherwise transfer such Shares to that Proposed Transferee at the
Offered Price or at a higher price, provided that such sale or other transfer is
consummated within 120 days after the date of the Notice, that any such sale or
other transfer is effected in accordance with any applicable securities laws and
that the Proposed Transferee agrees in writing that the provisions of this
Section shall continue to apply to the Shares in the hands of such Pro-posed
Transferee. If the Shares described in the Notice are not transferred to the
Proposed Transferee within such period, a new Notice shall be given to the
Company, and the Company and/or its assignees shall again be offered the Right
of First Refusal before any Shares held by the Holder may be sold or otherwise
transferred.

            (f) Exception for Certain Family Transfers. Anything to the contrary
contained in this Section notwithstanding, the transfer of any or all of the
Shares during the Optionee's lifetime or on the Optionee's death by will or
intestacy to the Optionee's immediate family or a trust for the benefit of the
Optionee's immediate family shall be exempt from the provisions of this Section.
"Immediate Family" as used herein shall mean spouse, lineal descendant or
antecedent, father, mother, brother or sister. In such case, the transferee or
other recipient shall receive and hold the Shares so transferred subject to the
provisions of this Section, and there shall be no further transfer of such
Shares except in accordance with the terms of this Section.

            (g) Termination of Right of First Refusal. The Right of First
Refusal shall terminate as to any Shares upon the first sale of Common Stock of
the Company to the general public pursuant to a registration statement filed
with and declared effective by the Securities and Exchange Commission under the
Securities Act of 1933, as amended.

      6. Tax Consultation. Optionee understands that Optionee may suffer adverse
tax consequences as a result of Optionee's purchase or disposition of the
Shares. Optionee represents that Optionee has consulted with any tax consultants
Optionee deems advisable in connection with the

                                      A-2
<PAGE>

purchase or disposition of the Shares and that Optionee is not relying on the
Company for any tax advice.

      7. Restrictive Legends and Stop-Transfer Orders.

            (a) Legends. Optionee understands and agrees that the Company shall
cause the legends set forth below or legends substantially equivalent thereto,
to be placed upon any certificate(s) evidencing ownership of the Shares together
with any other legends that may be required by the Company or by state or
federal securities laws:

            (b) THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE OFFERED, SOLD OR OTHERWISE
TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT
OR, IN THE OPINION OF COMPANY COUNSEL SATISFACTORY TO THE ISSUER OF THESE
SECURITIES, SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN
COMPLIANCE THEREWITH.

            (c) THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
CERTAIN RESTRICTIONS ON TRANSFER AND A RIGHT OF FIRST REFUSAL HELD BY THE ISSUER
OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE BETWEEN THE ISSUER AND
THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF WHICH MAY BE OBTAINED AT THE
PRINCIPAL OFFICE OF THE ISSUER. SUCH TRANSFER RESTRICTIONS AND RIGHT OF FIRST
REFUSAL ARE BINDING ON TRANSFEREES OF THESE SHARES.

            (d) IT IS UNLAWFUL TO CONSUMMATE A SALE OR TRANSFER OF THIS
SECURITY, OR ANY INTEREST THEREIN, OR TO RECEIVE ANY CONSIDERATION THEREFOR,
WITHOUT THE PRIOR WRITTEN CONSENT OF THE COMMISSIONER OF CORPORATIONS OF THE
STATE OF CALIFORNIA, EXCEPT AS PERMITTED IN THE COMMISSIONER'S RULES.

            (e) Optionee understands that transfer of the Shares may be
restricted by Section 260.141.11 of the Rules of the California Corporations
Commissioner, a copy of which is attached to Exhibit B, the Investment
Representation Statement.

            (f) Stop-Transfer Notices. Optionee agrees that, in order to ensure
compliance with the restrictions referred to herein, the Company may issue
appropriate "stop transfer" instructions to its transfer agent, if any, and
that, if the Company transfers its own securities, it may make appropriate
notations to the same effect in its own records.

            (g) Refusal to Transfer. The Company shall not be required (i) to
transfer on its books any Shares that have been sold or otherwise transferred in
violation of any of the provisions of this Exercise Notice or (ii) to treat as
owner of such Shares or to accord the right to vote or pay dividends to any
purchaser or other transferee to whom such Shares shall have been so
transferred.

                                      A-3
<PAGE>

      8. Successors and Assigns. The Company may assign any of its rights under
this Exercise Notice to single or multiple assignees, and this Exercise Notice
shall inure to the benefit of the successors and assigns of the Company. Subject
to the restrictions on transfer herein set forth, this Exercise Notice shall be
binding upon Optionee and his or her heirs, executors, administrators,
successors and assigns.

      9. Interpretation. Any dispute regarding the interpretation of this
Exercise Notice shall be submitted by Optionee or by the Company forthwith to
the Administrator which shall review such dispute at its next regular meeting.
The resolution of such a dispute by the Administrator shall be final and binding
on all parties.

      10. Governing Law: Severability. This Exercise Notice is governed by the
internal substantive laws but not the choice of law rules, of California.

      11. Entire Agreement. The Plan and Option Agreement are incorporated
herein by reference. This Exercise Notice, the Plan, the Option Agreement and
the Investment Representation Statement constitute the entire agreement of the
parties with respect to the subject matter hereof and supersede in their
entirety all prior undertakings and agreements of the Company and Optionee with
respect to the subject matter hereof, and may not be modified adversely to the
Optionee's interest except by means of a writing signed by the Company and
Optionee.

Submitted by:                                     Accepted by:

OPTIONEE                                          XENOPORT, MC.

__________________________                        _____________________________
Signature                                         By

__________________________                        _____________________________
Print Name                                        Its

Address of Residence:                             Address:

__________________________                        _____________________________
__________________________                        _____________________________
__________________________                        _____________________________

                                                  _____________________________
                                                  Date Received

                                      A-4
<PAGE>

                                                                    Exhibit 10.6

                                    EXHIBIT B

                       INVESTMENT REPRESENTATION STATEMENT

OPTIONEE:

COMPANY:      XENOPORT, INC.

SECURITY:     COMMON STOCK

AMOUNT:

DATE:

      In connection with the purchase of the above-listed Securities, the
undersigned Optionee represents to the Company the following:

                  (a) Optionee is aware of the Company's business affairs and
financial condition and has acquired sufficient information about the Company to
reach an informed and knowledgeable decision to acquire the Securities. Optionee
is acquiring these Securities for investment for Optionee's own account only and
not with a view to, or for resale in connection with, any "distribution" thereof
within the meaning of the Securities Act of 1933, as amended (the "Securities
Act").

                  (b) Optionee acknowledges and understands that the Securities
constitute "restricted securities" under the Securities Act and have not been
registered under the Securities Act in reliance upon a specific exemption
therefrom, which exemption depends upon, among other things, the bona fide
nature of Optionee's investment intent as expressed herein. In this connection,
Optionee understands that, in the view of the Securities and Exchange
Commission, the statutory basis for such exemption may be unavailable if
Optionee's representation was predicated solely upon a present intention to hold
these Securities for the minimum capital gains period specified under tax
statutes, for a deferred sale, for or until an increase or decrease in the
market price of the Securities, or for a period of one year or any other fixed
period in the future. Optionee further understands that the Securities must be
held indefinitely unless they are subsequently registered under the Securities
Act or an exemption from such registration is available. Optionee further
acknowledges and understands that the Company is under no obligation to register
the Securities. Optionee understands that the certificate evidencing the
Securities will be imprinted with a legend which prohibits the transfer of the
Securities unless they are registered or such registration is not required in
the opinion of counsel satisfactory to the Company, legend prohibiting their
transfer without the consent of the Commissioner of Corporations of the State of
California or and any other legend required under applicable state securities
laws.

                  (c) Optionee is familiar with the provisions of Rule 701 and
Rule 144, each promulgated under the Securities Act, which, in substance, permit
limited public resale of "restricted securities" acquired, directly or
indirectly from the issuer thereof, in a non-public offering subject to the
satisfaction of certain conditions. Rule 701 provides that if the issuer
qualifies under Rule 701 at the


<PAGE>

time of the grant of the Option to the Optionee, the exercise will be exempt
from registration under the Securities Act. In the event the Company becomes
subject to the reporting requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, ninety (90) days thereafter (or such longer period as any
market stand-off agreement may require) the Securities exempt under Rule 701 may
be resold, subject to the satisfaction of certain of the conditions specified by
Rule 144, including: (1) the resale being made through a broker in an
unsolicited "broker's transaction" or in transactions directly with a market
maker (as said term is defined under the Securities Exchange Act of 1934); and,
in the case of an affiliate, (2) the availability of certain public information
about the Company, (3) the amount of Securities being sold during any three
month period not exceeding the limitations specified in Rule 144(e), and (4) the
timely filing of a Form 144, if applicable.

      In the event that the Company does not qualify under Rule 701 at the time
of grant of the Option, then the Securities may be resold in certain limited
circumstances subject to the provisions of Rule 144, which requires the resale
to occur not less than one year after the later of the date the Securities were
sold by the Company or the date the Securities were sold by an affiliate of the
Company, within the meaning of Rule 144; and, in the case of acquisition of the
Securities by an affiliate, or by a non-affiliate who subsequently holds the
Securities less than two years, the satisfaction of the conditions set forth in
sections (1), (2), (3) and (4) of the paragraph immediately above.

                  (d) Optionee further understands that in the event all of the
applicable requirements of Rule 701 or 144 are not satisfied, registration under
the Securities Act, compliance with Regulation A, or some other registration
exemption will be required; and that, notwithstanding the fact that Rules 144
and 701 are not exclusive, the Staff of the Securities and Exchange Commission
has expressed its opinion that persons proposing to sell private placement
securities other than in a registered offering and otherwise than pursuant to
Rules 144 or 701 will have a substantial burden of proof in establishing that an
exemption from registration is available for such offers or sales, and that such
persons and their respective brokers who participate in such transactions do so
at their own risk. Optionee understands that no assurances can be given that any
such other registration exemption will be available in such event.

                  (e) Optionee understands that the certificate evidencing the
Securities will be imprinted with a legend which prohibits the transfer of the
Securities without the consent of the Commissioner of Corporations of
California. Optionee has read the applicable Commissioner's Rules with respect
to such restriction, a copy of which is attached.

                                                Signature of Optionee:

                                                ________________________________

                                                Date: __________________________

                                      B-2
<PAGE>

                                                                    Exhibit 10.6

                                  ATTACHMENT 1

              STATE OF CALIFORNIA - CALIFORNIA ADMINISTRATIVE CODE

         Title 10. Investment - Chapter 3. Commissioner of Corporations

260.141.11 : Restriction on Transfer.

      (a) The issuer of any security upon which a restriction on transfer has
been imposed pursuant to Sections 260.102.6, 260.141.10 or 260.534 shall cause a
copy of this section to be delivered to each issuee or transferee of such
security at the time the certificate evidencing the security is delivered to the
issuee or transferee.

      (b) It is unlawful for the holder of any such security to. consummate a
sale or transfer of such security, or any interest therein, without the prior
written consent of the Commissioner (until this condition is removed pursuant to
Section 260.141.12 of these rules), except:

            (1) to the issuer;

            (2) pursuant to the order or process of any court;

            (3) to any person described in Subdivision (i) of Section 25102 of
the Code or Section 260.105.14 of these rules;

            (4) to the transferor's ancestors, descendants or spouse, or any
custodian or trustee for the account of the transferor or the transferor's
ancestors, descendants, or spouse; or to a transferee by a trustee or custodian
for the account of the transferee or the transferee's ancestors, descendants or
spouse;

            (5) to holders of securities of the same class of the same issuer;

            (6) by way of gift or donation inter vivos or on death;

            (7) by or through a broker-dealer licensed under the Code (either
acting as such or as a finder) to a resident of a foreign state, territory or
country who is neither domiciled in this state to the knowledge of the
broker-dealer, nor actually present in this state if the sale of such securities
is not in violation of any securities law of the foreign state, territory or
country concerned;

            (8) to a broker-dealer licensed under the Code in a principal
transaction, or as an underwriter or member of an underwriting syndicate or
selling group;

            (9) if the interest sold or transferred is a pledge or other lien
given by the purchaser to the seller upon a sale of the security for which the
Commissioner's written consent is obtained or under this rule not required;

<PAGE>

            (10) by way of a sale qualified under Sections 25111, 25112, 25113
or 25121 of the Code, of the securities to be transferred, provided that no
order under Section 25140 or subdivision (a) of Section 25143 is in effect with
respect to such qualification;

            (11) by a corporation to a wholly owned subsidiary of such
corporation, or by a wholly owned subsidiary of a corporation to such
corporation;

            (12) by way of an exchange qualified under Section 25111 , 25112 or
25113 of the Code, provided that no order under Section 25140 or subdivision (a)
of Section 25143 is in effect with respect to such qualification;

            (13) between residents of foreign states, territories or countries
who are neither domiciled nor actually present in this state;

            (14) to the State Controller pursuant to the Unclaimed Property Law
or to the administrator of the unclaimed property law of another state; or

            (15) by the State Controller pursuant to the Unclaimed Property Law
or by the administrator of the unclaimed property law of another state if, in
either such case, such person (i) discloses to potential purchasers at the sale
that transfer of the securities is restricted under this rule, (ii) delivers to
each purchaser a copy of this rule, and (iii) advises the Commissioner of the
name of each purchaser;

            (16) by a trustee to a successor trustee when such transfer does not
involve a change in the beneficial ownership of the securities;

            (17) by way of an offer and sale of outstanding securities in an
issuer transaction that is subject to the qualification requirement of Section
25110 of the Code but exempt from that qualification requirement by subdivision
(f) of Section 25102; provided that any such transfer is on the condition that
any certificate evidencing the security issued to such transferee shall contain
the legend required by this section.

      (c) The certificates representing all such securities subject to such a
restriction on transfer, whether upon initial issuance or upon any transfer
thereof, shall bear on their face a legend, prominently stamped or printed
thereon in capital letters of not less than 10-point size, reading as follows:

      "IT IS UNLAWFUL TO CONSUMMATE A SALE OR TRANSFER OF THIS SECURITY, OR ANY
INTEREST THEREIN, OR TO RECEIVE ANY CONSIDERATION THEREFOR, WITHOUT THE PRIOR
WRITTEN CONSENT OF THE COMMISSIONER OF CORPORATIONS OF THE STATE OF CALIFORNIA,
EXCEPT AS PERMITTED IN THE COMMISSIONER'S RULES."

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