Crystalline catalase with a "Kat.f " of 43,000 was obtained as follows: 1. Adsorption on Al(OH)3 at pH 5.7, repeated washing of the adsorption complex with dil. acetate buffer at pH 5.5, and elution with M/10 phosphate buffer at pH 8.0. 2. Precipitation at pH 5.7 with 30 g. ammonium sulfate for every 100 cc. of enzyme soln. and repetition using 1/10 of initial vol. 3. Dialysis, followed by precipitation at pH 5.5 by enough alc. to make 40% cone. 4. Soln. in 1.25% NaCl and adsorption at pH 5.5 on A1(OH)3 followed by elution with phosphate buffer pH 8.0. 5. Precipitation of the eluted catalase with 30 g. of solid ammonium sulfate per 100 cc. at pH 5.7. The precipitate was mixed with a minute amt. of water, centrifuged and allowed to stand in the ice-chest. Erythrocyte eatalase gave a reddish-brown colored material identified as hemin with acetone and HC1.