<SEC-DOCUMENT>0000937556-18-000131.txt : 20180904
<SEC-HEADER>0000937556-18-000131.hdr.sgml : 20180904
<ACCEPTANCE-DATETIME>20180904174451
ACCESSION NUMBER:		0000937556-18-000131
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180830
FILED AS OF DATE:		20180904
DATE AS OF CHANGE:		20180904

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KIANI JOE E
		CENTRAL INDEX KEY:			0001228621

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-33642
		FILM NUMBER:		181053322

	MAIL ADDRESS:	
		STREET 1:		2400 BRIDGE PARKWAY
		CITY:			REDWOOD SHORES
		STATE:			CA
		ZIP:			940651166

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MASIMO CORP
		CENTRAL INDEX KEY:			0000937556
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTROMEDICAL & ELECTROTHERAPEUTIC APPARATUS [3845]
		IRS NUMBER:				330368882
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		52 DISCOVERY
		CITY:			IRVINE
		STATE:			CA
		ZIP:			92618
		BUSINESS PHONE:		949-297-7000

	MAIL ADDRESS:	
		STREET 1:		52 DISCOVERY
		CITY:			IRVINE
		STATE:			CA
		ZIP:			92618
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
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<DESCRIPTION>FORM 4
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        <issuerName>MASIMO CORP</issuerName>
        <issuerTradingSymbol>MASI</issuerTradingSymbol>
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            <rptOwnerStreet1>C/O MASIMO CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>52 DISCOVERY</rptOwnerStreet2>
            <rptOwnerCity>IRVINE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92618</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO and Chairman of the Board</officerTitle>
            <otherText></otherText>
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                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
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                </directOrIndirectOwnership>
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        </nonDerivativeHolding>
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            <securityTitle>
                <value>Common Stock</value>
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                <natureOfOwnership>
                    <value>See Footnote</value>
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        </nonDerivativeHolding>
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                <natureOfOwnership>
                    <value>See Footnote</value>
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            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Option (Right to Buy)</value>
            </securityTitle>
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                <transactionPricePerShare>
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            <exerciseDate>
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                <footnoteId id="F9"/>
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            <expirationDate>
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            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
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                <underlyingSecurityShares>
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                <value>2018-08-31</value>
            </transactionDate>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <transactionShares>
                    <value>126927</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>23.98</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
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                <footnoteId id="F9"/>
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            <expirationDate>
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            </expirationDate>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
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                </underlyingSecurityShares>
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                <sharesOwnedFollowingTransaction>
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                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
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        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Option (Right to Buy)</value>
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            </conversionOrExercisePrice>
            <transactionDate>
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            </transactionDate>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <transactionShares>
                    <value>6179</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>23.98</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2010-01-11</value>
                <footnoteId id="F9"/>
            </exerciseDate>
            <expirationDate>
                <value>2019-01-11</value>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6179.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The shares covered by this Form 4 were exercised and sold pursuant to a Rule 10b5-1 Sales Plan dated as of August 16, 2018, which is intended to comply with Rule 10b5-1 promulgated under the Securities Exchange Act of 1934, as amended.</footnote>
        <footnote id="F2">The price reported in Column 4 represents the weighted average sales price per share. The actual sales prices ranged from a low of $117.11 per share to a high of $118.67 per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer, or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.</footnote>
        <footnote id="F3">The price reported in Column 4 represents the weighted average sales price per share. The actual sales prices ranged from a low of $117.36 per share to a high of $118.73 per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer, or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.</footnote>
        <footnote id="F4">The price reported in Column 4 represents the weighted average sales price per share. The actual sales prices ranged from a low of $117.28 per share to a high of $119.48 per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer, or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.</footnote>
        <footnote id="F5">Shares held in four trusts for which Mr. Kiani is not the trustee.</footnote>
        <footnote id="F6">Shares held in one trust for which Mr. Kiani is the sole trustee.</footnote>
        <footnote id="F7">Shares held in Masimo Retirement Savings Plan.</footnote>
        <footnote id="F8">Shares held by an immediate family member for which Mr. Kiani exercises voting and investment control.</footnote>
        <footnote id="F9">This option was granted on January 11, 2009 and is exercisable as the option vests.  This option vested over a five year period, with 20% of the shares subject to the option vesting on each anniversary of the grant date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David J. Van Ramshorst, Attorney-In-Fact</signatureName>
        <signatureDate>2018-09-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
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</SEC-DOCUMENT>
