(1) An improved method of crystallization and recrystallization of beef liver catalase was described. (2) When the liver was autolysed at 25℃, the amount of extractive catalase increased by about 40 per cent during the first 20 hours, showing a maximum increasement. (3) By some modifications of the technique, crystalline catalase was obtained from the autolysate with a better yield. (4) By means of the solubility test, it was conclusively decided that the catalytic activity was essentially an attribute of the crystalline protein, and further the purity of the crystals as protein was confirmed. The author is grateful to Professor Yasuyoshi Oshima for his continued help and advice.