The regional concentrations and in-vitro secretions of canine pancreatic polypeptide (cPP), insulin, and glucagon were studied. CPP is found predominantly in the uncinate process of the dog pancreas, whereas insulin and, more markedly, glucagon predominate in the body and tail of the pancreas. In-vitro secretion studies of pancreatic pieces indicate that dibutyryl cyclic AMP (dcAMP) alone can stimulate cPP release whereas glucose and arginine alone have no effect. Arginine, but not glucose, potentiates this stimulant effect of dcAMP. These studies suggest that the cAMP generating system may play a role in regulation of cPP secretion.