Intravenously administered secretin stimulates pancreatic polypeptide (PP) release in patients with endocrine enteropancreatic tumors, but data in patients with nontumorous disorders are controversial. Therefore, we aimed to evaluate the plasma PP pattern after secretin administration in healthy subjects and in patients with gastroduodenal diseases investigated for recurrent ulcer disease and/or hypergastrinemia. Synthetic secretin was given as an intravenous bolus (2U/kg) in ten patients with Zollinger Ellison syndrome, ten with duodenal ulcer, ten with atropic gastritis and ten healthy volunteers. Blood samples were taken before and at regular intervals for 30min after secretin injection. Plasma PP and gastrin levels were measured by radioimmunoassay. Secretin promptly and significantly (P<0.01) increased PP plasma levels in all groups of subjects without any differences in peak values. There were no significant correlations between PP and gastrin plasma levels. Secretin at pharmacological doses is a powerful stimulus for PP release.