A hypoglycemic peptide, Polypeptide-p, was isolated from fruit, seeds and tissue of Momordica charantia (bitter gourd). Amino acid analysis indicates a minimum MW approximately 11,000 (166 residues). Polypeptide-p is a very effective hypoglycemic agent when administered s.c. to gerbils, langurs [Presbytis entillus] and humans. [Polypeptide-p may be useful in the treatment of diabetes mellitus.].