A method for isolation and perfusion of a pancreas preparation consisting of pancreas, stomach, proximal duodenum, and spleen is described. Basic characteristics of regulation of insulin secretion from the perfused pancreas isolated from rats, albino mice, obese mice (ob/ob), and black mice were identical. Viability and stability of the pancreas preparation during perfusion were maintained as documented by measurements of oxygen consumption of the pancreas preparation, perfusion pressure, and pH of the perfusion medium. The insulin-secretory capacity of the pancreas of different animal species was compared. Insulin secretion by the perfused rat and obese (ob/ob) mouse pancreas was much more potent than that by the pancreas of lean albino and lean black mice. D-Glucose-induced insulin secretion from the pancreas was decreased after fasting of the animals and was dependent on glucose concentration and presence of calcium in the perfusion medium. D-Glyceraldehyde, tolbutamide, D-mannose, dihydroxyacetone, L-leucine, and L-arginine also induced insulin secretion from the pancreas. D-Fructose, D-galactose, L-glucose, 3-O-methyl-D-glucose, N-acetylglucosamine, D-xylose, D,L-glyceric acid, pyruvate, L-lactate, and theophylline did not provoke insulin secretion.