Superoxide dismutase (SOD) was purified to homogeneity from fruiting bodies of edible mushroom, Lentinus edodes, by ammonium sulfate precipitation, diethylaminoethyl (DEAE)-Sepharose FF ion-exchange chromatography, Sephacryl S-200 gel filtration chromatography, and preparative PAGE. The molecular weight of the purified enzyme was estimated to be approximately 54 kDa by gel filtration chromatography, and the enzyme was shown to be consisted of two identical subunits of molecular weight 27 kDa by SDS-PAGE. The isoelectric point of the enzyme was 4.9 as determined by isoelectric focusing. The enzyme had optimal pH and temperature of pH 8.0 and $20^{circ}C$, respectively. The activity of the enzyme was inhibited by hydrogen peroxide, but inhibited less by cyanide and azide. The native enzyme was found to contain 0.89g-atom of iron, 0.75g-atom of zinc, and 0.46g-atom of copper per mol of enzyme. Analysis of amino acids composition revealed that the SOD from L. edodes contained a relatively large amount of glutamic acid/glutamine, proline, cysteine, isoleucine, and leucine, but only a small amount of aspartic acid/asparagine, tyrosine, and tryptophan when compared to the other iron-containing SODs.