BlackRock Municipal Bond Trust (the Trust) is a perpetual closed-end municipal bond fund. The Trust's investment objective is to provide current income exempt from regular federal income tax. The Trust will invest at least 80% of its total assets in municipal bonds that are investment-grade quality, or determined by the Trust's investment adviser to be of equivalent credit quality at time of purchase. The Trust may invest up to 20% of its total assets in municipal bonds that are rated, at the time of investment, Ba/BB or B by Moody's, Standard & Poor's or Fitch, or that are unrated but judged to be of comparable quality by its investment advisor. The Trust invests in sectors, such as health, county/city/special district/school district, housing, utilities, corporate, transportation, education and tobacco. BlackRock Advisors, LLC is the Trust's investment advisor. Its sub-advisor is BlackRock Financial Management, Inc.