Ownership Submission
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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(Print or Type Responses)
1. Name and Address of Reporting Person *
LASERSOHN JACK W
   2. Issuer Name and Ticker or Trading Symbol
MASIMO CORP [MASI] 		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)
C/O THE VERTICAL GROUP, L.P., 25 DEFOREST AVENUE		 3. Date of Earliest Transaction (Month/Day/Year)
05/14/2008
(Street)

SUMMIT, NJ 07901		 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 05/14/2008   S   20,000 (1) D $ 34.49 20,400 D  
Common Stock 05/14/2008   S   78,700 (1) D $ 34.49 78,782 I By Vertical Fund I, L.P. (2)
Common Stock 05/14/2008   S   48,600 (1) D $ 34.49 48,575 I By Vertical Fund II, L.P. (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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
LASERSOHN JACK W
C/O THE VERTICAL GROUP, L.P.
25 DEFOREST AVENUE
SUMMIT, NJ 07901		   X      

Signatures

 /s/ Jack W. Lasersohn   05/15/2008
**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 shares were sold pursuant to a Rule 10b5-1 trading plan.
(2) Mr. Lasersohn is a member and manager of The Vertical Group GP, LLC, a limited liability company that, through other entities, controls the investment decisions made on behalf of Vertical Fund I, L.P. and Vertical Fund II, L.P. (collectively, the "Funds"), and Mr. Lasersohn may therefore be deemed to be a beneficial owner of the shares owned by the Funds. Mr. Lasersohn disclaims beneficial ownership of the shares owned by the Funds except to the extent of his indirect pecuniary interest therein. This report shall not be deemed an admission that Mr. Lasersohn is the beneficial owner of such shares for purposes of Section 16 or for any other purpose.

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