Extracellular mannanase from Bacillus subtilis NM-39, an isolate from Philippine soil, was purified about 240-fold with a yield of 7.3% by ammonium sulphate fractionation, DEAE-Toyopearl chromatography and Sephacryl S-200 gel filtration. Its M r was 38 kDa and it had a pI of 4.8 and optimum activity at pH 5.0 and 55°C. It was stable at pH 4 to 9 and below 55°C. The amino acid composition of the enzyme was in the order Gly>Glx>Ser and Asx>Ala.