A pressor enzyme, renin, was purified about 60-fold by chromatography on an affinity column including pepstatin-aminohexyl-agarose with a high yield of 83% from the homogenate of adult mouse submaxillary glands. The renin obtained by the one-step purification was electrophoretically homogenous on SDS-polyacrylamide gel and was as active as an absolutely pure renin. The renin purified by the affinity column could be separated into five active components by chromatography on CM-cellulose. Each of these renins gave a symmetrical elution profile on the CM-cellulose column and a discrete protein band on polyacrylamide gel electrophoresis at pH 8.6. Administration of nanogram quantities of each of the two major renin fractions to nephrectomized rats caused a sustained rise of blood pressure and decrease in sensitivity of the animal to angiotensin II. This rapid and large-scale purification method using pepstatin-aminohexyl-agarose eliminates all four fractionation steps reported previously for the isolation of mouse submaxillary gland renin.