FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN 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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1. Name and Address of Reporting Person * NELSON GLEN D   2. Issuer Name and Ticker or Trading Symbol Cardiovascular Systems Inc [CSII] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 651 CAMPUS DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 05/09/2013 (Street) ST. PAUL, MN 55112 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 05/09/2013   P   8,393 A $ 17.9938 (1) 406,585 D   Common Stock 05/13/2013   P   10,000 A $ 18.2117 (2) 416,585 D   Common Stock               28,500 I By Family Trust (3) Common Stock               258,655 I Held by LLC (4)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Underlying Securities (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (right to buy)	$ 12.37							(5)	11/30/2015	Common Stock	9,705		9,705	D
Stock Option (right to buy)	$ 9.28							(5)	11/30/2014	Common Stock	6,470		6,470	D
Stock Option (right to buy)	$ 8.83							(5)	12/18/2016	Common Stock	12,940		12,940	D
Stock Option (right to buy)	$ 7.9							(5)	10/08/2017	Common Stock	4,322		4,322	D
Stock Option (right to buy)	$ 11.38							(5)	11/12/2017	Common Stock	15,087		15,087	D
Warrant	$ 9.28							09/12/2008	09/12/2013	Common Stock	53,916		53,916	I	Held by LLC (4)
Warrant	$ 8.83							02/25/2009	02/24/2014	Common Stock	56,558		56,558	I	Held by LLC (4)
Warrant (right to buy)	$ 9.28							11/30/2010	09/12/2013	Common Stock	117,399		117,399	I	Held by LLC (4)
Warrant (right to buy)	$ 8.83							11/30/2010	02/24/2014	Common Stock	452,729		452,729	I	Held by LLC (4)
Restricted Stock Units	(6)							(6)	(6)	Common Stock	5,714		5,714	D
Restricted Stock Units	(6)							(6)	(6)	Common Stock	11,628		11,628	D
Restricted Stock Units	(6)							(6)	(6)	Common Stock	21,739		21,739	D
Restricted Stock Units	(6)							(6)	(6)	Common Stock	7,192		7,192	D
Restricted Stock Units	(7)							(7)	(7)	Common Stock	10,917		10,917	D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
NELSON GLEN D 651 CAMPUS DRIVE ST. PAUL, MN 55112	X

Signatures

/s/ Alexander Rosenstein as Attorney-in-Fact for Glen D. Nelson pursuant to Power of Attorney previously filed.		05/13/2013
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(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)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $17.85 to $18.00 inclusive. The reporting person undertakes to provide Cardiovascular Systems, Inc., any security holder of Cardiovascular Systems, Inc. or the staff of the Securities and Exchange Commission upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
(2)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.18 to $18.23 inclusive. The reporting person undertakes to provide Cardiovascular Systems, Inc., any security holder of Cardiovascular Systems, Inc. or the staff of the Securities and Exchange Commission upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
(3)	Shares are held by the Glen D. Nelson 2012 Family Trust for the benefit of Dr. Nelson's wife and descendants.
(4)	Shares are held by GDN Holdings, LLC, of which Dr. Nelson is the sole owner.
(5)	Fully exercisable.
(6)	Each restricted stock unit represents the right to receive a payment from CSI equal in value to the market price per share of CSI common stock on the date of payment, and will be payable in cash or shares of the Company's Common Stock beginning six months following the termination of the reporting person's board membership.
(7)	Each restricted stock unit represents the right to receive a payment from CSI equal in value to the market price per share of CSI common stock on the date of payment, and will be payable in cash or shares of the Company's common stock beginning six months following the termination of the reporting person's board membership; provided, however, that the restricted stock units vest in quarterly amounts of 2,730 on each of 9/30/2012, and 2,729 on 12/31/2012, 3/31/2013, and 6/30/2013.

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