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 *
  US VENTURE PARTNERS X LP
2. Date of Event Requiring Statement (Month/Day/Year)
03/13/2014
3. Issuer Name and Ticker or Trading Symbol
CASTLIGHT HEALTH, INC. [CSLT]
(Last)
(First)
(Middle)
2735 SAND HILL ROAD
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)

MENLO PARK, CA 94025
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)
Class A Common Stock 19,551
D (4)
 
Class A Common Stock 625
I
Directly owned by AFF X (4)

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 Preferred Stock (1)   (2)   (3) Class A Common Stock 130,339 $ 0 D (4)  
Series A1 Preferred Stock (1)   (2)   (3) Class A Common Stock 51,223 $ 0 D (4)  
Series C Preferred Stock (1)   (2)   (3) Class A Common Stock 1,649,919 $ 0 D (4)  
Series D Preferred Stock (1)   (2)   (3) Class A Common Stock 489,752 $ 0 D (4)  
Series A Preferred Stock (1)   (2)   (3) Class A Common Stock 4,170 $ 0 I Directly owned by AFF X (4)
Series A1 Preferred Stock (1)   (2)   (3) Class A Common Stock 1,639 $ 0 I Directly owned by AFF X (4)
Series C Preferred Stock (1)   (2)   (3) Class A Common Stock 52,784 $ 0 I Directly owned by AFF X (4)
Series D Preferred Stock (1)   (2)   (3) Class A Common Stock 15,668 $ 0 I Directly owned by AFF X (4)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
US VENTURE PARTNERS X LP
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
USVP X AFFILIATES LP
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
FEDERMAN IRWIN
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
KRAUSZ STEVEN M
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
Lewis Richard W.
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
Matteucci Paul A
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
ROOT JONATHAN D
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    
Tansey Casey M
2735 SAND HILL ROAD
MENLO PARK, CA 94025
    X    

Signatures

Michael P. Maher 03/13/2014
**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) The Series A, Series A1, Series C and Series D Convertible Preferred Stock will automatically convert into Class A Common Stock on a one-for-one basis immediately prior to the completion of the Issuer's initial public offering.
(2) The securities are immediately convertible.
(3) The expiration date is not relevant to the conversion of these securities.
(4) The reported securities are owned directly by each of U.S. Venture Partners X, L.P. ("USVP X") and USVP X Affiliates Fund, L.P. ("AFF X") and together with USVP X and AFF X, the "USVP X Funds"). Presidio Management Group X, LLC ("PMG X") is the general partner of each of USVP X and AFF X and may be deemed to have sole voting and dispositive power over the shares held by the USVP X Funds. PMG X and each of Irwin Federman, Steven M. Krausz, Richard W. Lewis, Paul A Matteucci, Jonathan D. Root and Casey M. Tansey, the managing members of PMG X, may be deemed to share voting and dispositive power over the reported shares. Such persons and entities disclaim beneficial ownership of shares held by the USVP X Funds, except to the extent of any proportionate pecuniary interest therein.

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