In order to examine the possibility that the urinary excretion of histidylleucine might reflect the in vivo biogenesis of angiotensin, a technique has been devised for the detection of histidyl peptides in normal human urine. The peptides are isolated by displacement procedures on ion-exchange resins and further analyzed by paper and ion-exchange column chromatography. Histidyl peptides have been quantitated by fluorescence analysis after reaction with o-phthalaldehyde. Histidylleucine, in quantities of about 5–25 μg, has been shown to be present in 24-hour collections of human urine. The peptide isolated from urine has been found to be identical with synthetic material in comparisons using high resolution ion-exchange chromatography, paper chromatography in four solvent systems, acid hydrolysis followed by amino acid analysis, and fluorescence spectrum. A histidyl peptide which was regularly present, usually in somewhat larger quantities, was a tripeptide with sequence His-Leu-Gly or His-Gly-Leu. Numerous other histidyl peptides were present in smaller amounts but did not correspond to any of several other simple histidyl dipeptides examined and were not further identified.