0000891092-11-003276.txt : 20110517 0000891092-11-003276.hdr.sgml : 20110517 20110516214713 ACCESSION NUMBER: 0000891092-11-003276 CONFORMED SUBMISSION TYPE: 497 PUBLIC DOCUMENT COUNT: 1 FILED AS OF DATE: 20110517 DATE AS OF CHANGE: 20110516 EFFECTIVENESS DATE: 20110517 FILER: COMPANY DATA: COMPANY CONFORMED NAME: BLACKROCK MUNICIPAL BOND FUND, INC. CENTRAL INDEX KEY: 0000225635 IRS NUMBER: 132896246 STATE OF INCORPORATION: NJ FISCAL YEAR END: 0630 FILING VALUES: FORM TYPE: 497 SEC ACT: 1933 Act SEC FILE NUMBER: 002-57354 FILM NUMBER: 11849638 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: MERRILL LYNCH MUNICIPAL BOND FUND INC DATE OF NAME CHANGE: 19920703 FORMER COMPANY: FORMER CONFORMED NAME: ONE LIBERTY MUNICIPAL BOND FUND INC DATE OF NAME CHANGE: 19780622

0000225635 S000002334 BlackRock National Municipal Fund

C000006118 Investor A

C000006119 Investor B

C000006120 Investor C1

C000006121 Institutional

C000038033 Investor C

497 1 e43605_497.htm SUPPLEMENT

BLACKROCK MUNICIPAL BOND FUND, INC.
BlackRock National Municipal Fund
(the “Fund”)

Supplement dated May 16, 2011
to the Prospectus and Statement of Additional Information, dated May 16, 2011

Service Shares of the Fund are currently closed to all purchases. Service Shares of the Fund will be available for purchase by eligible investors upon the closing of a proposed reorganization transaction (the “Reorganization”) between the Fund and BlackRock AMT-Free Municipal Bond Portfolio (the “Target Fund”), a series of BlackRock Funds II. The closing of the Reorganization, which is expected to occur following the close of business on July 15, 2011, is contingent upon approval by the shareholders of the Target Fund.

Shareholders should retain this Supplement for future reference.

Code: PR&SAI-NM-0511SUPSVC