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 * Camber Capital Management LLC   2. Issuer Name and Ticker or Trading Symbol Cardiovascular Systems Inc [CSII] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 101 HUNTINGTON AVENUE, SUITE 2101 3. Date of Earliest Transaction (Month/Day/Year) 09/19/2016 (Street) BOSTON, MA 02199 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 09/19/2016 09/19/2016 S   1,043,000 D $ 23.2501 3,057,000 I See Footnotes (1) (2) Common Stock 09/20/2016 09/20/2016 S   57,000 D $ 23.5376 3,000,000 I See Footnotes (1) (3) (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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Camber Capital Management LLC 101 HUNTINGTON AVENUE SUITE 2101 BOSTON, MA 02199		X

Signatures

/s/Stephen DuBois		09/21/2016
**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)	Securities reported herein for Camber Capital Management LLC (the "LLC" ) represent Common Stock beneficially owned and held of record by Camber Capital Master Fund, L.P. (the "Master Fund"), another private investment fund (the "Fund") and one managed account (the "Managed Account") for which the LLC serves as the investment manager. Stephen DuBois is the managing member of the LLC and managing member of the general partner for the Fund and the Master Fund. The LLC, the Master Fund, the Fund, the Managed Account, general partner and Mr. DuBois (the "Reporting Persons") are each beneficial owners and have an address of 101 Huntington Avenue, Floor 21, Boston, MA 02199. The Reporting Persons disclaim beneficial ownership, within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise of such portion of the shares in which the Reporting Persons have no actual pecuniary interest therein.
(2)	Of the securities reported for this transaction, 1,012,462 shares of Common Stock were sold for the account of the Master Fund, 6,453 shares of Common Stock were sold for the account of the Fund, and 24,085 shares of Common Stock were sold for the account of the Managed Account.
(3)	Of the securities reported for this transaction, 55,331 shares of Common Stock were sold for the account of the Master Fund, 353 shares of Common Stock were sold for the account of the Fund, and 1,316 shares of Common Stock were sold for the account of the Managed Account.
(4)	As of the closing of trading on September 20, 2016, 2,912,165 shares of Common Stock were held for the account of the Master Fund, 18,559 shares of Common Stock were held for the account of the Fund, and 69,276 shares of Common Stock were held for the account of the Managed Account.

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