    <SEC-DOCUMENT>0001193125-18-212847-index.html : 20180705
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    <ACCEPTANCE-DATETIME>20180705110430
    ACCESSION NUMBER:		0001193125-18-212847
    CONFORMED SUBMISSION TYPE:	N-CSR
    PUBLIC DOCUMENT COUNT:		25
    CONFORMED PERIOD OF REPORT:	20180430
    FILED AS OF DATE:		20180705
    DATE AS OF CHANGE:		20180705
    EFFECTIVENESS DATE:		20180705

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			BLACKROCK MUNIASSETS FUND, INC.
    		CENTRAL INDEX KEY:			0000901243
    		IRS NUMBER:				223239638
    		STATE OF INCORPORATION:			MD
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		N-CSR
    		SEC ACT:		1940 Act
    		SEC FILE NUMBER:	811-07642
    		FILM NUMBER:		18939806

    	BUSINESS ADDRESS:
    		STREET 1:		100 BELLEVUE PARKWAY
    		CITY:			WILMINGTON
    		STATE:			DE
    		ZIP:			19809
    		BUSINESS PHONE:		800-441-7762

    	MAIL ADDRESS:
    		STREET 1:		100 BELLEVUE PARKWAY
    		CITY:			WILMINGTON
    		STATE:			DE
    		ZIP:			19809

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	MUNIASSETS FUND INC
    		DATE OF NAME CHANGE:	19930714

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	MUNIINCOME FUND INC
    		DATE OF NAME CHANGE:	19930517
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>N-CSR
    <SEQUENCE>1
    <FILENAME>d559615dncsr.htm
    <DESCRIPTION>BLACKROCK MUNIASSETS FUND, INC
    <TEXT>
    Document 1 - file: d559615dncsr.htm

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    <DOCUMENT>
    <TYPE>EX-99.CERT
    <SEQUENCE>2
    <FILENAME>d559615dex99cert.htm
    <DESCRIPTION>CERTIFICATIONS PURSUANT TO SECTION 302
    <TEXT>
    Document 2 - file: d559615dex99cert.htm

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    <DOCUMENT>
    <TYPE>EX-99.906CERT
    <SEQUENCE>3
    <FILENAME>d559615dex99906cert.htm
    <DESCRIPTION>CERTIFICATIONS PURSUANT TO SECTION 906
    <TEXT>
    Document 3 - file: d559615dex99906cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.PROXY.POL
    <SEQUENCE>4
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    <DESCRIPTION>CLOSED-END FUND PROXY VOTING POLICY
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    <DESCRIPTION>GLOBAL CORPORATE GOVERNANCE AND ENGAGEMENT PRINCIPALS
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    <DESCRIPTION>GRAPHIC
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