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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13G


                    Under the Securities Exchange Act of 1934

                                  ISORAY, INC.
------------------------------------------------------------------------------
                                (Name of Issuer)

                    COMMON STOCK, PAR VALUE $0.001 PER SHARE
------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    46489V104
                                 (CUSIP Number)

                                 AUGUST 17, 2006
------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

              Rule 13d-1(b)
        X     Rule 13d-1(c)
              Rule 13d-1(d)

*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for any  subsequent  amendment  containing  information  which  would  alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).






CUSIP No. 46489V104

      1. Names of Reporting Persons.
           I.R.S. Identification Nos. of above persons (entities only).

           MicroCapital Fund LP
           52-2286453

      2. Check the Appropriate Box if a Member of a Group (See Instructions)

           (a) [   ] .........................................................

           (b) [   ] .........................................................

      3.   SEC Use Only.......................................................

           ...................................................................

      4.   Citizenship or Place of Organization  Delaware.....................

Number of      5. Sole Voting Power...........................................
Shares Bene-
ficially by    6. Shared Voting Power 1,600,000...............................
Owned by Each
Reporting      7. Sole Dispositive Power......................................
Person With:
               8. Shared Dispositive Power  1,600,000.........................

      9. Aggregate Amount Beneficially Owned by Each Reporting Person 1,600,000

      10.   Check if the Aggregate Amount in Row (9) Excludes Certain Shares
      (See Instructions)......................................................

      11.   Percent of Class Represented by Amount in Row (9)    8.88%........

      12. Type of Reporting Person (See Instructions) PN .

...............................................................................

...............................................................................

...............................................................................

...............................................................................

...............................................................................

...............................................................................










Item 1.

      (a)   Name of Issuer

            IsoRay, Inc.

      (b)   Address of Issuer's Principal Executive Offices

            350 Hills Street, Suite 106
            Richland, WA 99354

Item 2.

      (a)   Name of Person Filing

            This statement is being filed by MicroCapital Fund, LP (the
            "Reporting Person").

      (b) Address of Principal Business Office or, if none, Residence

            MicroCapital Fund LP's principal place of business is located at:
            623 Fifth Avenue, Suite 2502, New York, New York 10022

      (c)   Citizenship

            Item 4 of the cover page is incorporated by reference.

      (d)   Title of Class of Securities

            Common Stock, par value $0.001 per share

      (e)   CUSIP Number

            46489V104



Item 3. If this statement is filed pursuant to ss.ss.240.13d-1(b) or
240.13d-2(b) or (c), check whether the person filing is a:

      (a)   _____ Broker or dealer registered under section 15 of the Act
                  (15 U.S.C. 78o).

      (b)   _____ Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

      (c)   _____ Insurance company as defined in section 3(a)(19) of the Act
                  (15 U.S.C. 78c).

      (d)   _____ Investment company registered under section 8 of the
                  Investment Company Act of 1940 (15 U.S.C. 80a-8).

      (e)   _____ An investment adviser in accordance with
                  ss.240.13d-1(b)(1)(ii)(E);

      (f)   _____ An employee benefit plan or endowment fund in accordance
                  with ss.240.13d-1(b)(1)(ii)(F);

      (g)   _____ A parent holding company or control person in accordance
                  with ss. 240.13d-1(b)(1)(ii)(G);

      (h)   _____ A savings associations as defined in Section 3(b) of the
                  Federal Deposit Insurance Act (12 U.S.C. 1813);

      (i)   _____ A church plan that is excluded from the definition of an
                  investment company under section 3(c)(14) of the Investment
                  Company Act of 1940 (15 U.S.C. 80a-3);

      (j)   _____ Group, in accordance with ss.240.13d-1(b)(1)(ii)(J).



Item 4.  Ownership.

      Provide the following information regarding the aggregate number and
percentage of the class of securities of the issuer identified in Item 1.

      (a) Amount beneficially owned: 1,600,000.

      (b) Percent of class: 8.88%.

      (c) Number of shares as to which the person has:

            (i) Sole power to vote or to direct the vote _______.

            (ii) Shared power to vote or to direct the vote 1,600,000.

            (iii) Sole power to dispose or to direct the disposition of ______.

            (iv) Shared power to dispose or to direct the disposition
                 of 1,600,000.



Item 5.  Ownership of Five Percent or Less of a Class

     If this  statement  is being  filed to report  the fact that as of the date
hereof the reporting  person has ceased to be the beneficial  owner of more than
five percent of the class of securities, check the following _____.



Item 6.  Ownership of More than Five Percent on Behalf of Another Person.

      Not applicable.


Item 7.  Identification and Classification of the Subsidiary Which Acquired
         the Security Being Reported on By the Parent Holding Company

      Not applicable.



Item 8.  Identification and Classification of Members of the Group

      Not applicable.



Item 9. Notice of Dissolution of Group

      Not applicable.



Item 10. Certification

     By signing  below I certify  that,  to the best of my knowledge and belief,
     the securities referred to above were acquired and are held in the ordinary
     course of business  and were not  acquired and are not held for the purpose
     of or with the effect of changing or influencing  the control of the issuer
     of the securities and were not acquired and are not held in connection with
     or as a participant in any transaction having that purpose or effect.




                                    SIGNATURE

     After  reasonable  inquiry and to the best of my  knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.



Dated August 22, 2006


                              MICROCAPITAL FUND LP

                              /s/  Ian P. Ellis
                              ------------------------------------------------
                              Ian P. Ellis, Managing Member, MicroCapital LLC,
                              General Partner of MicroCapital Fund LP


Attention:  Intentional  misstatements  or omissions of fact constitute  Federal
criminal violations (See 18 U.S.C. 1001)






                                    EXHIBIT A


            Identification and Classification of Members of the Group

Pursuant to Rule  13d-1(b)(ii)(J)  and Rule 13d-1(k)(1) under the Securities and
Exchange  Act of 1934,  the members of the group  making  this joint  filing are
identified and classified as follows:

                Name                             Classification