Manganese peroxidase (MnP) was isolated from the culture filtrate of the wood log mushroom Stereum ostrea (S. ostrea), grown on Koroljova medium, and then purified by ammonium sulfate [70% (w/v)] fractionation, DEAEcellulose anion exchange chromatography, and Sephadex G-100 column chromatography, with an attainment of 88.6-fold purification and the recovery of 22.8% of initial activity. According to SDS-PAGE the molecular mass of the MnP was 40 kDa. The optimal pH and temperature were found to be 4.5 and 35oC, respectively. The enzyme was stable even after exposure to a pH range of 4.5 to 6.0, and at temperatures of up to 35oC at a pH of 4.5 for 1h. The Km and Vmax values for the substrate phenol red were found to be 8 ?m and 111.14 U/mg of protein, respectively. The MnP also oxidized other substrates such as guaiacol, DMP, and veratryl alcohol. Sodium azide, EDTA, SDS, Cu2+, and Fe2+, at 1-5 mM, strongly inhibited enzyme activity, whereas Ca2+ and Zn2+ increased enzyme activity. The participation of the purified enzyme in the decolorization of dyes suggests that S. ostrea manganese peroxidase could be effectively employed in textile industries.