Erythrocyte catalase of a Japanese-type acatalasemia case and a normal control subject was separated by chromatofocusing with or without prior partial purification with DEAE cellulose and analyzed by polyacrylamide gradient gel electrophoresis. Two bands of catalase activity were found in the partially purified preparations with molecular weights of 29×10(4) and 35×10(4) in the acatalasemia case and of 28×10(4) and 36×10(4) in the normal control. The molecular weight of normal catalase in untreated hemolysate was 25×10(4). With normal catalase, chromatofocusing fractionation caused a shift toward higher molecular species in the alkaline range eluates from the untreated hemolysate and an opposite shift toward lower molecular weight species in the same pH range eluates from the partially purified preparation. Normal catalase could be identified as protein bands on polyacrylamide gradient gel with hemolysate fractionated by chromatofocusing. Possible application of this technigne in the study of acatalasemia protein with a sensitive protein stain was suggested.