An affinity gel for the purification of renin was prepared by coupling pepstatin to aminohexylagarose gel. Partially purified human renin (Haas et al., Arch. Biochem. Biophys., 110, 534-543, 1965) was purified further by affinity chromatography on the pepstatin-aminohexyl-agarose gel, gel filtration on a Sephadex G-75 column, and ion exchange chromatography on a DEAE-cellulose column. Separation from a protease permitted further purification without progressive loss of activity. Three peaks of enzymatically active renin were obtained after the DEAE-cellulose chromatography, with specific activities ranging from 206 to 166 and 85 Goldblatt units/mg protein, respectively. The specific activity of 206 GU units/mg represents a 103,000-fold purification compared to the renin present in the first crude extract.