Abstract:The isozymes of superoxide dismutase (SOD) in leaves of wheat and peanut were investigated and identified by isoelectric focusing gel electrophoresis. The total four bands were found in wheat leaves, among them the band with the highest mobility was proved to be the chloroplastic SOD, the others with intermediate mobilities were probably cytoplasmic SODs. It was observed that there was apparent difference between patterns of SOD isozymes from leaves of wild and cultivated peanut. Leaves of wild peanut contain three different types of SOD isozyme (band A, band B and band C). Band A and B were cyanide-sensitive, hence they should be Cu-Zn-SOD. Band C was cyanide- insensitive and might be Mn-SOD located in mitochondria. The major part of SOD activity in cultivated peanut leaves was concentrated in chloroplasts, and it was cyanide-sensitive. The experiments of SOD activity inhibition by KCN showed that leaves of cultivated peanut contained more Cu-Zn-SOD. On the contrary, the percentage of non-Cu-Zn-SOD was highter in wild species than in cultivated. The PI values of distinct bands were determined and the significance of this study for the further evaluation of resistance of peanut plant is discussed.