According to animal studies pancreastatin (PST), a peptide that is secreted by numerous neroendocrine cells, inhibits insulin secretion and has a hyperglycaemic and glycogenolytic effect. However, physiologic role of PST in carbohydrate metabolism remains unclear. In order to determine the best stimulus of PST secretion, four different stimulations of GI tract were carried out in 10 healthy volunteers: oral glucose loading test, intravenous glucose loading test, intravenous glucagon infusion and standard meal loading test. Serum PST concentration was measured radioimmunologically at established intervals after each stimulation. It was found that either oral or intravenous glucose loading test do not increase serum PST concentration; intravenous glucagon infusion decreases serum PST concentration and a standard meal increases serum PST concentration.