Renin was completely purified from human kidney cortex using a rapid 3-step procedure which included homogenization and ammonium sulfate precipitation, aminohexyl pepstatin affinity chromatography, and affinity chromatography using a synthetic octapeptide renin inhibitor (H-77) with a reduced peptide bond between Leu5 - Leu6. Three kg of cortex dissected from 10 kg of human cadaver kidney yielded 0.7 mg protein with a specific activity of 1123 GU/mg protein and an overall recovery of 52%. Both gel filtration high pressure liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) revealed a molecular weight of 44,000, although 22,000 and 18,000 molecular weight bands were also identified by SDS PAGE. Amino terminal sequencing demonstrated a leucine residue at the 1 position indicating that prorenin is converted to renin following cleavage at the carboxyl end of two dibasic residues, Lys-2-Arg-1. Sequencing of the first 19 amino acids was in agreement with the sequence deduced from human renin cDNA sequence.