1ISR_sc13g.txt 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) November 22, 2010 (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). Page 1 of 10 Pages CUSIP No. 46489V104 13G Page 2 of 10 Pages ----------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS Hudson Bay Master Fund Ltd. ----------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [X] -------------------------------------------------------------------------------- (3) SEC USE ONLY -------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands -------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER 0 SHARES ----------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* OWNED BY -------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING -------------------------------------------------------------- PERSON WITH: (8) SHARED DISPOSITIVE POWER 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* ----------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* ----------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ----------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 9.90% (see Item 4)* ----------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) CO ----------------------------------------------------------------------------- * As more fully described in Item 4, certain of these reported securities are subject to a 9.9% blocker and the percentage set forth in row (11) gives effect to such blocker. However, as more fully described in Item 4, the securities reported in rows (6), (8) and (9) show the number of shares of Common Stock that would be issuable upon full exercise of such reported securities and do not give effect to such blocker. Therefore, the actual number of shares of Common Stock beneficially owned by such Reporting Person, after giving effect to such blocker, is less than the number of securities reported in rows (6), (8) and (9). CUSIP No. 46489V104 13G Page 3 of 10 Pages ----------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS Hudson Bay Capital Management, L.P. ----------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [X] ----------------------------------------------------------------------------- (3) SEC USE ONLY ----------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER 0 SHARES -------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* OWNED BY -------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING -------------------------------------------------------------- PERSON WITH: (8) SHARED DISPOSITIVE POWER 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* ----------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* ----------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ----------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 9.90% ----------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN ----------------------------------------------------------------------------- * As more fully described in Item 4, certain of these reported securities are subject to a 9.9% blocker and the percentage set forth in row (11) gives effect to such blocker. However, as more fully described in Item 4, the securities reported in rows (6), (8) and (9) show the number of shares of Common Stock that would be issuable upon full exercise of such reported securities and do not give effect to such blocker. Therefore, the actual number of shares of Common Stock beneficially owned by such Reporting Person, after giving effect to such blocker, is less than the number of securities reported in rows (6), (8) and (9). CUSIP No. 46489V104 13G Page 4 of 10 Pages ----------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS Sander Gerber ----------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [ ] (b) [X] ----------------------------------------------------------------------------- (3) SEC USE ONLY ----------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION United States -------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER 0 SHARES -------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* OWNED BY -------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING -------------------------------------------------------------- PERSON WITH: (8) SHARED DISPOSITIVE POWER 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* ----------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,101,333 shares of Common Stock Warrants (Series A) to purchase up to 666,667 shares of Common Stock, which expire on 2/22/2011 (see Item 4)* Warrants (Series B) to purchase up to 562,500 shares of Common Stock, which expire on 5/24/2011 (see Item 4)* Warrants (Series C) to purchase up to 2,812,500 shares of Common Stock, which expire on 11/24/2015 (see Item 4)* ----------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ----------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 9.90% (See Item 4) ----------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN ----------------------------------------------------------------------------- * As more fully described in Item 4, certain of these reported securities are subject to a 9.9% blocker and the percentage set forth in row (11) gives effect to such blocker. However, as more fully described in Item 4, the securities reported in rows (6), (8) and (9) show the number of shares of Common Stock that would be issuable upon full exercise of such reported securities and do not give effect to such blocker. Therefore, the actual number of shares of Common Stock beneficially owned by such Reporting Person, after giving effect to such blocker, is less than the number of securities reported in rows (6), (8) and (9). CUSIP No. 46489V104 13G Page 5 of 10 Pages ----------------------------------------------------------------------------- Item 1. (a) Name of Issuer IsoRay, Inc. a Minnesota corporation (the "Company") (b) Address of Issuer's Principal Executive Offices 350 Hills Street Suite 106 Richland, Washington 99354 Item 2(a). Name of Person Filing This statement is filed by Hudson Bay Master Fund Ltd., Hudson Bay Capital Management, L.P. (the "Investment Manager") and Mr. Sander Gerber ("Mr. Gerber"), who are collectively referred to herein as "Reporting Persons." Item 2(b). Address of Principal Business Office or, if none, Residence The address of the principal business office of each of the Reporting Persons is: 120 Broadway, 40th Floor New York, NY 10271 The address of the principal business office of Hudson Bay Master Fund Ltd. is: Walkers SPV Limited, Walker House PO Box 908GT, Mary Street Georgetown, Grand Cayman Cayman Islands Item 2(c). Citizenship Citizenship is set forth in Row 4 of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person. Item 2(d) Title of Class of Securities Common Stock, par value $0.001 per share (the "Common Stock") Item 2(e) CUSIP Number 46489V104 CUSIP No. 46489V104 13G Page 6 of 10 Pages ----------------------------------------------------------------------------- Item 3. If this statement is filed pursuant to 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 association 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 Rule 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. The information required by Items 4(a) - (c) is set forth in Rows 5 - 11 of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person. On the date of event which requires the filing of this Schedule 13G the Reporting Persons may have been deemed to be the beneficial owners of more than five percent of the Common Stock. The Company's Prospectus filed pursuant to Rule 424(b)(5) on November 24, 2010, indicates that the total number of outstanding shares of Common Stock upon completion of the offering made pursuant to such Prospectus is 25,804,325. The percentages set forth on Row ll of the cover page for each Reporting Person is based on the Company's outstanding Common Stock and assumes the partial exercise of the reported warrants up to the blocker (as defined below). CUSIP No. 46489V104 13G Page 7 of 10 Pages ----------------------------------------------------------------------------- Pursuant to the terms of the reported warrants (the Reported Warrants), the Reporting Persons cannot exercise any of the Reported Warrants until such time as the Reporting Persons would not beneficially own, after any such exercise, more than 9.9% of the outstanding shares of Common Stock (the Blocker). As of the date hereof, each of the Reporting Persons may be deemed the beneficial owner of 2,147,198 shares of Common Stock held by Hudson Bay Master Fund Ltd. As of the date hereof, Hudson Bay Master Fund Ltd. also holds the Reported Warrants, however, at this time, the Reporting Persons are not able to fully exercise the Reported Warrants due to the Blocker. In addition to the Reported Warrants, Hudson Bay Master Fund Ltd. holds additional Series D warrants to purchase up to 2,812,500 shares of Common Stock which are not exercisable until May 24, 2011 and are only exercisable on or after such date to the extent that the Series C Warrants held by Hudson Bay Master Fund Ltd. are not exercisable due to the NYSE Amex Equities blocker contained herein (the Additional Warrants). Pursuant to the terms of the Additional Warrants, the Reporting Persons cannot exercise any of the Additional Warrants until such time as the Reporting Persons would not beneficially own, after any such exercise, more than 9.9% of the outstanding shares of Common Stock. The Investment Manager, which serves as the investment manager to Hudson Bay Master Fund Ltd., may be deemed to be the beneficial owner of all shares of Common Stock held by Hudson Bay Master Fund Ltd.. Mr. Gerber serves as the managing member of Hudson Bay Capital GP LLC, which is the general partner of the Investment Manager. Each of Hudson Bay Master Fund Ltd. and Mr. Gerber disclaims beneficial ownership of these securities. Hudson Bay Master Fund Ltd. is named as Reporting Person herein solely to report the securities held in its name. 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 See Exhibit I. Item 9. Notice of Dissolution of Group Not applicable. CUSIP No. 46489V104 13G Page 8 of 10 Pages ----------------------------------------------------------------------------- Item 10. Certification By signing below each of the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above 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. Exhibits: Exhibit I: Joint Filing Agreement, dated as of November 30, 2010, by and among Hudson Bay Master Fund, Ltd., Hudson Bay Capital Management, L.P., and Sander Gerber. CUSIP No. 46489V104 13G Page 9 of 10 Pages ----------------------------------------------------------------------------- SIGNATURES After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information with respect to it set forth in this statement is true, complete, and correct. Dated: November 30, 2010 HUDSON BAY CAPITAL MANAGEMENT, L.P. By: /s/ Sander Gerber Name: Sander Gerber Title: Authorized Signatory HUDSON BAY MASTER FUND LTD By: Hudson Bay Capital Management, L.P. Investment Manager By: /s/ SANDER GERBER Name: Sander Gerber Title: Authorized Signatory /s/ Sander Gerber SANDER GERBER CUSIP No. 46489V104 13G Page 10 of 10 Pages EXHIBIT I JOINT FILING AGREEMENT This will confirm the agreement by and among the undersigned that the Schedule 13G filed with the Securities and Exchange Commission on or about the date hereof with respect to the beneficial ownership by the undersigned of the Common Stock, par value $0.001 per share of IsoRay, Inc is being filed, and all amendments thereto will be filed, on behalf of each of the persons and entities named below in accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended. 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. Dated as of November 30, 2010 HUDSON BAY MASTER FUND LTD HUDSON BAY CAPITAL MANAGEMENT, L.P. By: Hudson Bay Capital Management, L.P. By: /s/ Sander Gerber Name: Sander Gerber Investment Manager Title: Authorized Signatory By: /s/ Sander Gerber Name: Sander Gerber Name: Sander Gerber Title: Authorized Signatory /s/ Sander Gerber SANDER GERBER DOC ID-14810291.3