The complete amino acid sequence of sauvagine, a new active polypeptide from the skin of Phyllomedusa sauvagei, a frog of Central and South America, has been determined by automated liquid-phase procedure after specific removal of the N-terminal pyrrolidonecarboxylic acid, and specific cleavages at the single methionine and at the two arginine residues. The proposed sequence is: Pyr-Gly-Pro-Pro-Ile-Ser-Ile-Asp-Leu-Ser-Leu-Glu-Leu-Leu-Arg-Lys-Met-Ile-Glu-Ile -Glu-Lys-Gln-Glu-Lys-Glu-Lys-Gln-Gln-Ala-Ala-Asn-Asn-Arg-Leu-Leu-Leu-Asp-Thr-Il e-NH2. Sauvagine possesses a number of pharmacological actions on diuresis, the cardiovascular system and endocrine glands; it can be considered the prototype of a new family of amphibian peptides, in addition to the tachykinins, bradykinins, dermorphins, caerulein-like and bombesin-like peptides.