Exhibit 10.21

                                 PROMISSORY NOTE

$25,000                                                            July 14, 2006


     FOR VALUE RECEIVED, Intraop Medical Corporation, a Nevada corporation (the
"Maker"), with its primary offices located at 570 Del Rey Avenue, Sunnyvale, CA
94085, promises to pay to the order of Bushido Capital Master Fund, LP, or its
registered assigns (the "Payee"), upon the terms set forth below, the principal
sum of Twenty Five Thousand Dollars ($25,000).

1.   Payments. The full amount of principal under this Note shall be due on
August 14, 2006 (the "Maturity Date"), unless due earlier in accordance with the
terms of this Note.

2.   Events of Default.

     (a) "Event of Default", wherever used herein, means any one of the
     following events (whatever the reason and whether it shall be voluntary or
     involuntary or effected by operation of law or pursuant to any judgment,
     decree or order of any court, or any order, rule or regulation of any
     administrative or governmental body):

          (i) any default in the payment of the principal of this Note, as and
          when the same shall become due and payable;

          (ii) Maker shall fail to observe or perform any obligation or shall
          breach any term or provision of this Note and such failure or breach
          shall not have been remedied within five days after the date on which
          notice of such failure or breach shall have been delivered;

          (iii) Maker or any of its subsidiaries shall fail to observe or
          perform any of their respective obligations owed to Payee or any other
          covenant, agreement, representation or warranty contained in, or
          otherwise commit any breach hereunder or in any other agreement
          executed in connection herewith;

          (iv) Maker or any of its subsidiaries shall commence, or there shall
          be commenced against Maker or any subsidiary a case under any
          applicable bankruptcy or insolvency laws as now or hereafter in effect
          or any successor thereto, or Maker or any subsidiary commences any
          other proceeding under any reorganization, arrangement, adjustment of
          debt, relief of debtors, dissolution, insolvency or liquidation or
          similar law of any jurisdiction whether now or hereafter in effect
          relating to Maker or any subsidiary, or there is commenced against
          Maker or any subsidiary any such bankruptcy, insolvency or other
          proceeding which remains undismissed for a period of 60 days; or Maker
          or any subsidiary is adjudicated insolvent or bankrupt; or any order
          of relief or other order approving any such case or proceeding is
          entered; or Maker or any subsidiary suffers any appointment of any
          custodian or the like for it or any substantial part of its property
          which continues undischarged or unstayed for a period of 60 days; or
          Maker or any subsidiary makes a general assignment for the benefit of
          creditors; or Maker or any subsidiary shall fail to pay, or shall
          state that it is unable to pay, or shall be unable to pay, its debts
          generally as they become due; or Maker or any subsidiary shall call a
          meeting of its creditors with a view to arranging a composition,
          adjustment or restructuring of its debts; or Maker or any subsidiary
          shall by any act or failure to act expressly indicate its consent to,
          approval of or acquiescence in any of the foregoing; or any corporate
          or other action is taken by Maker or any subsidiary for the purpose of
          effecting any of the foregoing;


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          (v) Maker or any subsidiary shall default in any of its respective
          obligations under any other note or any mortgage, credit agreement or
          other facility, indenture agreement, factoring agreement or other
          instrument under which there may be issued, or by which there may be
          secured or evidenced any indebtedness for borrowed money or money due
          under any long term leasing or factoring arrangement of Maker or any
          subsidiary, whether such indebtedness now exists or shall hereafter be
          created and such default shall result in such indebtedness becoming or
          being declared due and payable prior to the date on which it would
          otherwise become due and payable; or

          (vi) Maker shall (a) be a party to any Change of Control Transaction
          (as defined below), (b) agree to sell or dispose all or in excess of
          40% of its assets in one or more transactions (whether or not such
          sale would constitute a Change of Control Transaction), (c) redeem or
          repurchase more than a de minimis number of shares of Common Stock or
          other equity securities of Maker, or (d) make any distribution or
          declare or pay any dividends (in cash or other property, other than
          common stock) on, or purchase, acquire, redeem, or retire any of
          Maker's capital stock, of any class, whether now or hereafter
          outstanding. "Change of Control Transaction" means the occurrence of
          any of: (i) an acquisition after the date hereof by an individual or
          legal entity or "group" (as described in Rule 13d-5(b)(1) promulgated
          under the Securities Exchange Act of 1934, as amended) of effective
          control (whether through legal or beneficial ownership of capital
          stock of Maker, by contract or otherwise) of in excess of 40% of the
          voting securities of Maker, (ii) a replacement at one time or over
          time of more than one-half of the members of Maker's board of
          directors which is not approved by a majority of those individuals who
          are members of the board of directors on the date hereof (or by those
          individuals who are serving as members of the board of directors on
          any date whose nomination to the board of directors was approved by a
          majority of the members of the board of directors who are members on
          the date hereof), (iii) the merger of Maker with or into another
          entity that is not wholly-owned by Maker, consolidation or sale of 40%
          or more of the assets of Maker in one or a series of related
          transactions, or (iv) the execution by Maker of an agreement to which
          Maker is a party or by which it is bound, providing for any of the
          events set forth above in (i), (ii) or (iii).

     (b) If any Event of Default occurs, the full principal amount of this Note
     shall become, at the Payee's election, immediately due and payable in cash.
     Commencing 5 days after the occurrence of any Event of Default that results
     in the acceleration of this Note, the interest rate on this Note shall
     accrue at the rate of 18% per annum, or such lower maximum amount of
     interest permitted to be charged under applicable law. The Payee need not
     provide and Maker hereby waives any presentment, demand, protest or other
     notice of any kind, and the Payee may immediately and without expiration of
     any grace period enforce any and all of its rights and remedies hereunder
     and all other remedies available to it under applicable law. Such
     declaration may be rescinded and annulled by Payee at any time prior to
     payment hereunder. No such rescission or annulment shall affect any
     subsequent Event of Default or impair any right consequent thereon.

3.   Warrant Exercise. The Payee shall have the right, in its sole discretion,
to cancel amounts owed to it by the Maker under this Note in lieu of the payment
of cash for the exercise of any warrants to purchase Common Stock of the Maker
held by the Payee. Maker hereby agrees to accept the cancellation of amounts
owed hereunder as payment of any such exercise price under any warrants to
purchase Common Stock of the Maker held by the Payee.


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<PAGE>

4.   No Waiver of Payee's Rights. All payments hereunder shall be made without
setoff, deduction or counterclaim. No delay or failure on the part of the Payee
in exercising any of its options, powers or rights, nor any partial or single
exercise of its options, powers or rights shall constitute a waiver thereof or
of any other option, power or right, and no waiver on the part of the Payee of
any of its options, powers or rights shall constitute a waiver of any other
option, power or right. Maker hereby waives presentment of payment, protest, and
all notices or demands in connection with the delivery, acceptance, performance,
default or endorsement of this Note. Acceptance by the Payee of less than the
full amount due and payable hereunder shall in no way limit the right of the
Payee to require full payment of all sums due and payable hereunder in
accordance with the terms hereof.

5.   Modifications. No term or provision contained herein may be modified,
amended or waived except by written agreement or consent signed by the party to
be bound thereby.

6.   Cumulative Rights and Remedies; Usury. The rights and remedies of Payee
expressed herein are cumulative and not exclusive of any rights and remedies
otherwise available under this Note or applicable law (including at equity). The
election of Payee to avail itself of any one or more remedies shall not be a bar
to any other available remedies, which Maker agrees Payee may take from time to
time. If it shall be found that any interest due hereunder shall violate
applicable laws governing usury, the applicable rate of interest due hereunder
shall be reduced to the maximum permitted rate of interest under such law.

7.   Collection Expenses. If Payee shall commence an action or proceeding to
enforce this Note, then Maker shall reimburse Payee for its costs of collection
and reasonable attorneys fees incurred with the investigation, preparation and
prosecution of such action or proceeding.

8.   Severability. If any provision of this Note is declared by a court of
competent jurisdiction to be in any way invalid, illegal or unenforceable, the
balance of this Note shall remain in effect, and if any provision is
inapplicable to any person or circumstance, it shall nevertheless remain
applicable to all other persons and circumstances.

9.   Successors and Assigns. This Note shall be binding upon Maker and its
successors and shall inure to the benefit of the Payee and its successors and
assigns. The term "Payee" as used herein, shall also include any endorsee,
assignee or other holder of this Note.

10.  Lost or Stolen Promissory Note. If this Note is lost, stolen, mutilated or
otherwise destroyed, Maker shall execute and deliver to the Payee a new
promissory note containing the same terms, and in the same form, as this Note.
In such event, Maker may require the Payee to deliver to Maker an affidavit of
lost instrument and customary indemnity in respect thereof as a condition to the
delivery of any such new promissory note.

11.  Due Authorization. This Note has been duly authorized, executed and
delivered by Maker and is the legal obligation of Maker, enforceable against
Maker in accordance with its terms. No consent of any other party and no
consent, license, approval or authorization of, or registration or declaration
with, any governmental authority, bureau or agency is required in connection
with the execution, delivery or performance by the Maker, or the validity or
enforceability of this Note other than such as have been met or obtained. The
execution, delivery and performance of this Note and all other agreements and
instruments executed and delivered or to be executed and delivered pursuant
hereto or thereto or the securities issuable upon conversion of this will not
violate any provision of any existing law or regulation or any order or decree
of any court, regulatory body or administrative agency or the certificate of
incorporation or by-laws of the Maker or any mortgage, indenture, contract or
other agreement to which the Maker is a party or by which the Maker or any
property or assets of the Maker may be bound.


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<PAGE>

12.  Governing Law. All questions concerning the construction, validity,
enforcement and interpretation of this Note shall be governed by and construed
and enforced in accordance with the internal laws of the State of New York,
without regard to the principles of conflicts of law thereof. Each of Maker and
Payee agree that all legal proceedings concerning the interpretations,
enforcement and defense of this Note shall be commenced in the state and federal
courts sitting in the City of New York, Borough of Manhattan (the "New York
Courts"). Each of Maker and Payee hereby irrevocably submit to the exclusive
jurisdiction of the New York Courts for the adjudication of any dispute
hereunder (including with respect to the enforcement of this Note), and hereby
irrevocably waives, and agrees not to assert in any suit, action or proceeding,
any claim that it is not personally subject to the jurisdiction of any such
court, that such suit, action or proceeding is improper. Each of Maker and Payee
hereby irrevocably waive personal service of process and consents to process
being served in any such suit, action or proceeding by mailing a copy thereof
via registered or certified mail or overnight delivery (with evidence of
delivery) to the other at the address in effect for notices to it under this
Note and agrees that such service shall constitute good and sufficient service
of process and notice thereof. Nothing contained herein shall be deemed to limit
in any way any right to serve process in any manner permitted by law. Each of
Maker and Payee hereby irrevocably waive, to the fullest extent permitted by
applicable law, any and all right to trial by jury in any legal proceeding
arising out of or relating to this Note or the transactions contemplated hereby.

13.  Notice. Any and all notices or other communications or deliveries to be
provided by the Payee hereunder, shall be in writing and delivered personally,
by facsimile, sent by a nationally recognized overnight courier service or sent
by certified or registered mail, postage prepaid, addressed to the Maker, 570
Del Rey Avenue, Sunnyvale, CA 94085, or such other address or facsimile number
as the Maker may specify for such purposes by notice to the Payee delivered in
accordance with this paragraph. Any and all notices or other communications or
deliveries to be provided by the Maker hereunder shall be in writing and
delivered personally, by facsimile, sent by a nationally recognized overnight
courier service or sent by certified or registered mail, postage prepaid,
addressed to each Payee at the address of such Payee appearing on the books of
the Maker, or if no such address appears, at the principal place of business of
the Payee. Any notice or other communication or deliveries hereunder shall be
deemed given and effective on the earliest of (i) the date of transmission if
delivered by hand or by telecopy that has been confirmed as received by 5:00
P.M. on a business day, (ii) one business day after being sent by nationally
recognized overnight courier or received by telecopy after 5:00 P.M. on any day,
or (iii) five business days after being sent by certified or registered mail,
postage and charges prepaid, return receipt requested.

     The undersigned signs this Note as a maker and not as a surety or guarantor
or in any other capacity.

                             INTRAOP MEDICAL CORPORATION

                                           /s/ Donald A. Goer
                                           ------------------
                                           Donald A. Goer
                                           President & CEO
                                           Intraop Medical Corporation


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