-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 BshygHF0ZJfuNrl7y2E3NIiJACraztnM+JaeO8KpuFc/sa1tVaW98t3ZY8BQGKnp
 2PUcwpw2ehUNi1GVwIo6tQ==

<SEC-DOCUMENT>0000072162-10-000001.txt : 20100520
<SEC-HEADER>0000072162-10-000001.hdr.sgml : 20100520
<ACCEPTANCE-DATETIME>20100520102417
ACCESSION NUMBER:		0000072162-10-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100519
FILED AS OF DATE:		20100520
DATE AS OF CHANGE:		20100520

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MOORE CECIL H JR
		CENTRAL INDEX KEY:			0001265101

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-00640
		FILM NUMBER:		10846883

	MAIL ADDRESS:	
		STREET 1:		5430 LBJ FREEWAY SUITE 1700
		CITY:			DALLAS
		STATE:			TX
		ZIP:			75240

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NL INDUSTRIES INC
		CENTRAL INDEX KEY:			0000072162
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INORGANIC CHEMICALS [2810]
		IRS NUMBER:				135267260
		STATE OF INCORPORATION:			NJ
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		5430 LBJ FREEWAY
		STREET 2:		SUITE 1700
		CITY:			DALLAS
		STATE:			TX
		ZIP:			75240-2697
		BUSINESS PHONE:		972-233-1700

	MAIL ADDRESS:	
		STREET 1:		5430 LBJ FREEWAY
		STREET 2:		SUITE 1700
		CITY:			DALLAS
		STATE:			TX
		ZIP:			75240-2697

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	NATIONAL LEAD CO
		DATE OF NAME CHANGE:	19710520
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-05-19</periodOfReport>

    <issuer>
        <issuerCik>0000072162</issuerCik>
        <issuerName>NL INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>NL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001265101</rptOwnerCik>
            <rptOwnerName>MOORE CECIL H JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5430 LBJ FREEWAY, SUITE 1700</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75240</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock $0.125 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2010-05-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares issued for no cash consideration to nonemployee directors under the NL Industries, Inc. 1998 Long-Term Incentive Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>A. Andrew R. Louis, Attorney-in-fact, for Cecil H. Moore, Jr.</signatureName>
        <signatureDate>2010-05-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----