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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-04-28</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>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0001</value>
            </securityTitle>
            <transactionDate>
                <value>2017-04-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>181154</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6574196</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Acuitas Group Holdings, LLC</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0001</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <transactionDate>
                <value>2017-04-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2385111</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8959307</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Crede CG III, Ltd.</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.0001</value>
                <footnoteId id="F5"/>
            </securityTitle>
            <transactionDate>
                <value>2017-04-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F5"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>233735</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9193042</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These securities were purchased by Acuitas Group Holdings, LLC (&quot;Acuitas&quot;) in connection with a public offering by the issuer pursuant to a Registration Statement on Form S-1 (Registration No. 333-216007).</footnote>
        <footnote id="F2">The reporting person is the Managing Director of Acuitas 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">In July 2015, Catasys, Inc., a Delaware corporation (the &quot;Company&quot;) entered into a $3.56 million, 12% Original Issue Discount Convertible Debenture due January 18, 2016 (the &quot;July 2015 Convertible Debenture&quot;) with Crede CG III, Ltd. (&quot;Crede&quot;). On April 28, 2017, Crede converted $4,293,198.01 principal amount of the July 2015 Convertible Debenture into 2,385,111 shares of the Company's common stock at the applicable conversion price.</footnote>
        <footnote id="F4">The reporting person is the Managing Director of Crede and may be deemed to beneficially own or control the securities.  The reporting person disclaims beneficial ownership of any such securities.</footnote>
        <footnote id="F5">Terren Peizer deferred part of his salary in the amount of $1.1 million for the 2016 and 2015 years.  On April 28, 2017, the Company issued 233,734 shares to Mr. Peizer as payment of such deferred salary.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Terren S. Peizer</signatureName>
        <signatureDate>2017-05-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
