<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-12-21</periodOfReport>

    <issuer>
        <issuerCik>0001136174</issuerCik>
        <issuerName>CATASYS, INC.</issuerName>
        <issuerTradingSymbol>CATS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000904534</rptOwnerCik>
            <rptOwnerName>PEIZER TERREN S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>11601 WILSHIRE BLVD #1100</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90025</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <officerTitle>Chairman &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Warrant to purchase</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.10</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-12-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1022835</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2016-12-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2021-12-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1022835</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1022835</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Acuitas Group Holdings, LLC</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Convertible Debenture</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.10</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-12-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2557088</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2016-12-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2017-03-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2557088</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2557088</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Acuitas Group Holdings, LLC</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On December 15, 2016, Catasys, Inc. (&quot;Catasys&quot;) issued to Acuitas Group Holdings, LLC (&quot;Acuitas&quot;) a warrant exercisable for 1,022,835 shares of Catasys common stock at an exercise price of $1.10 per share (the &quot;Warrant&quot;), subject to potential future adjustment pursuant to the terms of the Warrant.  The Warrant was issued to Acuitas concurrently and in connection with a debt financing, pursuant to which Catasys issued to Acuitas an 8% senior convertible debenture dated as of December 15, 2016 (the &quot;Convertible Debenture&quot;)</footnote>
        <footnote id="F2">The reporting person is the Managing Director and 100% owner of Acuitas Group Holdings, LLC, and may be deemed to beneficially own or control the securities. The reporting person disclaims beneficial ownership of any such securities.</footnote>
        <footnote id="F3">On December 15, 2016, Catasys issued the Convertible Debenture to Acuitas.  At the option of the holder, the Convertible Debenture is convertible into 2,557,088 shares of common stock at an exercise price of $1.10 per share, subject to potential future adjustment pursuant to the terms of the Convertible Debenture.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Terren S. Peizer</signatureName>
        <signatureDate>2016-12-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
