Peroxidase isozyme C was isolated from mung bean cotyledon and purified to homogeneity as ascertained by chromatography and polyacrylamide gel electrophoresis, and then crystal-sized. Purification procedures included ammonium sulfate precipitation and column chromatography on Sephadex G-75, DEAE-cellulose and DEAF-Sephadex A-50. Peroxidase isozyme C was purified about 63 fold with 5% recovery. Isozyme C showed optimal activity at pH 5.0 with o-dianisidine and at pH 6.0 with guaiacol as substrate, and the optimal temperature was 70℃. Molecular weight of 50,000 was estimated or for the isozyme C by SDS-polyacrylamide gel electrophoresis. At 70℃, it took 30 min to inactivate the isozyme to 50%, and at 80℃, this isozyme was almost completely inactivated in 20 min. The Km value of isozyme C for o-dianisidine was 0. 11mM and that for guaiacol was 60.98mM using hydrogen peroxide as cesubstrate, and the kinetic pattern showed a competitive cyanide inhibition with respect to substrate. The crystalline structure of isozyme C was rectangular in shape.