Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Mitsui & Co. Venture Partners II, L.P.
 2. Date of Event Requiring Statement (Month/Day/Year)
12/29/2008		 3. Issuer Name and Ticker or Trading Symbol
CARDIOVASCULAR SYSTEMS INC [CSII]
(Last)
(First)
(Middle)
200 PARK AVENUE, 36TH FLOOR, 		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

NEW YORK, NY 10166		 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Series A Redeemable Convertible Preferred Stock 07/28/2006   (4) Common Stock 678,713 $ 5.71 I See footnote (1)
Series A-1 Redeemable Convertible Preferred Stock 09/19/2007   (4) Common Stock 121,359 $ 8.5 I See footnote (2)
Series A Warrant 07/19/2006 07/19/2011 Series A Redeemable Convertible Preferred Stock 96,377 $ 5.71 I See footnote (3)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Mitsui & Co. Venture Partners II, L.P.
200 PARK AVENUE, 36TH FLOOR
NEW YORK, NY 10166		     X    
Mitsui & Co. Venture Partners, Inc.
200 PARK AVENUE, 36TH FLOOR
NEW YORK, NY 		       President and CEO  
MITSUI & CO LTD
2-1, OHTEMACHI 1-CHOME
CHIYODA-KU
TOKYO, M0 		       General Manager  

Signatures

/s/ Taro Inaba, Authorized Signatory for Mitsui & Co. Venture Partners II, L.P. 12/29/2008
**Signature of Reporting Person Date
/s/ Taro Inaba, President and CEO for Mitsui & Co. Venture Partners, Inc. 12/29/2008
**Signature of Reporting Person Date
/s/ Tsutomu Yoshida, General Manager for Mitsui & Co., Ltd 12/29/2008
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) 675,148 shares of the Series A Redeemable Convertible Preferred Stock are owned directly by Mitsui & Co. Venture Partners II, L.P. ("MCVP II") and indirectly by (i) Mitsui & Co. Venture Partners, Inc. ("MCVP"), the general partner of MCVP II and (ii) Mitsui & Co., Ltd. ("Mitsui"), the 100% indirect owner of MCVP II and MCVP. Each reporting person disclaims beneficial ownership of the reported securities except to the extent of such reporting person's pecuniary interest therein.
(2) 117,647 shares of the Series A-1 Redeemable Convertible Preferred Stock are owned directly by MCVP II and indirectly by (i) MCVP, the general partner of MCVP II and (ii) Mitsui, the 100% indirect owner of MCVP II and MCVP. Each reporting person disclaims beneficial ownership of the reported securities except to the extent of such reporting person's pecuniary interest therein.
(3) A Series A Warrant convertible into 96,377 shares of Series A Redeemable Convertible Preferred Stock is owned directly by MCVP II and indirectly by (i) MCVP, the general partner of MCVP II and (ii) Mitsui, the 100% indirect owner of MCVP II and MCVP. Each reporting person disclaims beneficial ownership of the reported securities except to the extent of such reporting person's pecuniary interest therein.
(4) This stock is convertible at any time and does not expire.

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