<SEC-DOCUMENT>0001084991-18-000004.txt : 20180126
<SEC-HEADER>0001084991-18-000004.hdr.sgml : 20180126
<ACCEPTANCE-DATETIME>20180126134559
ACCESSION NUMBER:		0001084991-18-000004
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180117
FILED AS OF DATE:		20180126
DATE AS OF CHANGE:		20180126

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Hazlett James R
		CENTRAL INDEX KEY:			0001340731

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31398
		FILM NUMBER:		18551091

	MAIL ADDRESS:	
		STREET 1:		2208 S.C.R. 1084 1/2
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79706

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATURAL GAS SERVICES GROUP INC
		CENTRAL INDEX KEY:			0001084991
		STANDARD INDUSTRIAL CLASSIFICATION:	OIL, GAS FIELD SERVICES, NBC [1389]
		IRS NUMBER:				752811855
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		508 WEST WALL STREET
		STREET 2:		SUITE 550
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79701
		BUSINESS PHONE:		432-262-2700

	MAIL ADDRESS:	
		STREET 1:		508 WEST WALL STREET
		STREET 2:		SUITE 550
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79701
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2018-01-17</periodOfReport>

    <dateOfOriginalSubmission>2018-01-17</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001084991</issuerCik>
        <issuerName>NATURAL GAS SERVICES GROUP INC</issuerName>
        <issuerTradingSymbol>ngs</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001340731</rptOwnerCik>
            <rptOwnerName>Hazlett James R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2208 S.C.R. 1084 1/2</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MIDLAND</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>79706</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP -- Technical Services</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-01-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1349</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>29.01</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45282</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On January 17, 2018, the reporting person filed a Form 4 reporting the sale of 1,688 shares of common stock. The reporting person's broker subsequently acknowledged that 339 of such 1,688 shares were erroneously sold by the broker. The sale of the 339 shares was unwound through the broker's error account and therefore did not occur for purposes of the reporting person's account. This Form 4 amends the foregoing transaction.  The remainder of the transactions reported in the January 17, 2018, Form 4 are unchanged and remain as originally reported.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>James R. Hazlett</signatureName>
        <signatureDate>2018-01-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
