PHI (PHI-27), has been discovered and isolated from porcine upper intestinal tissue by using a chemical method for finding peptide hormones and other active peptides. Porcine PHI was found in the intestinal extract by the presence of its COOH-terminal isoleucine amide structure. It consists of 27 amino acid residues and has the following amino acid sequence: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Arg-Leu-Leu-Gly-Gln-Leu-Ser-Ala-Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Ile-NH2. The remarkable sequence homology of PHI to the vasoactive intestinal peptide, secretin, glucagon, and gastric inhibitory polypeptide indicates that this peptide is a member of the glucagonsecretin family. PHI has several biological activities similar to those of vasoactive intestinal peptide and secretin.