X0101 EFFECT 33 LIVE 2006-10-02 0000891092-06-002937 485APOS 0000225635 BLACKROCK MUNICIPAL BOND FUND, INC. 002-57354 S000002332 BlackRock Municipal Insured Fund C000006110 Investor A S000002332 BlackRock Municipal Insured Fund C000006111 Investor B S000002332 BlackRock Municipal Insured Fund C000006112 Investor C1 S000002332 BlackRock Municipal Insured Fund C000006113 Institutional S000002332 BlackRock Municipal Insured Fund C000038032 Investor C S000002334 BlackRock National Municipal Fund C000006118 Investor A S000002334 BlackRock National Municipal Fund C000006119 Investor B S000002334 BlackRock National Municipal Fund C000006120 Investor C1 S000002334 BlackRock National Municipal Fund C000006121 Institutional S000002334 BlackRock National Municipal Fund C000038033 Investor C S000002335 BlackRock Short-Term Municipal Fund C000006122 Investor A1 S000002335 BlackRock Short-Term Municipal Fund C000006123 Investor B S000002335 BlackRock Short-Term Municipal Fund C000006124 Investor C S000002335 BlackRock Short-Term Municipal Fund C000006125 Institutional S000002335 BlackRock Short-Term Municipal Fund C000038034 Investor A S000002335 BlackRock Short-Term Municipal Fund C000038035 BlackRock S000002335 BlackRock Short-Term Municipal Fund C000038044 Service S000011867 BlackRock High Yield Municipal Fund C000032425 Investor A S000011867 BlackRock High Yield Municipal Fund C000032427 Investor C S000011867 BlackRock High Yield Municipal Fund C000032428 Institutional