SEC FORM 3

SEC Form 3

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
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

CAHILL EDWARD L

(Last)

(First)

(Middle)

C/O MASIMO CORPORATION, 40 PARKER

(Street)

IRVINE

92618

(City)

(State)

(Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
08/07/2007

3. Issuer Name and Ticker or Trading Symbol
MASIMO CORP [ MASI ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

5. If Amendment, Date of 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

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)
Common Stock	42,000	D
Common Stock	373,200	I	By Cahill, Warnock Strategic Partners Fund, L.P.⁽¹⁾

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: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Nonqualified Stock Option (right to buy)	⁽²⁾	05/22/2013	Common Stock	64,800	$2.75	D
Nonqualified Stock Option (right to buy)	⁽³⁾	10/02/2016	Common Stock	30,000	$11.56	D
Series A Preferred Stock	⁽⁴⁾	⁽⁴⁾	Common Stock	454,545⁽⁵⁾⁽⁶⁾	⁽⁴⁾	I	By Cahill, Warnock Strategic Partners Fund, L.P.⁽¹⁾
Series D Preferred Stock	⁽⁴⁾	⁽⁴⁾	Common Stock	857,145⁽⁵⁾⁽⁷⁾	⁽⁴⁾	I	By Cahill, Warnock Strategic Partners Fund, L.P.⁽¹⁾

Explanation of Responses:

1. Mr. Cahill may be deemed to have an indirect pecuniary interest as a partner of Cahill, Warnock Strategic Partners, L.P., the general partner of Cahill, Warnock Strategic Partners Fund, L.P, in these shares. Mr. Cahill disclaims beneficial ownership of the shares held by Cahill, Warnock Strategic Partners Fund, L.P. except to the extent of his pecuniary interest in these shares.

2. This option was granted on May 22, 2003 and is exercisable as the option vests. This option vests over a five-year period, with 20% of the shares subject to the option vesting on each anniversary of the grant date.

3. This option was granted on October 2, 2006. All of the shares subject to this option vest on December 31, 2007, 15 months following the grant date.

4. Each share of the Issuer's Preferred Stock will automatically convert into Common Stock immediately upon the closing of the Issuer's initial public offering, for no additional consideration.

5. Gives effect to the 3-for-1 forward stock split of the Common Stock effected on June 25, 2007.

6. Comprised of 151,515 shares held by Cahill, Warnock Strategic Partners Fund, L.P. which are convertible into 454,545 shares of Common Stock.

7. Comprised of 285,715 shares held by Cahill, Warnock Strategic Partners Fund, L.P. which are convertible into 857,145 shares of Common Stock.

	/s/ Mark P. de Raad, Attorney-in-Fact	08/07/2007
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
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