With a view toward the therapeutic use of somatostatin in the treatment of acute pancreatitis, a preliminary investigation was conducted with 6 healthy volunteers, in which the suppressive effect of somatostatin on endocrine and exocrine pancreatic function was observed. A 30-minute baseline measurement period was followed by the administration of cyclic somatostatin (100 microgram by i.v. injection plus a 90-minute infusion at a rate of 200 microgram/hr). After the first 45 minutes of this infusion secretion was submaximally stimulated by the infusion of secretin-cholecystokinin-pancreozymin (CCK-PZ) (75 U each), over two hours. No decrease was observed in basal bicarbonate or enzyme concentration under somatostatin administration alone. However, secretion did not show the usual steep rise after the commencement of stimulation. After the somatostatin infusion was stopped, i.e. under secretin-CCK-PZ alone, a significant increase occurred in the values of secretin-induced volume, bicarbonate concentration and total bicarbonate contents of the duodenal aspirate, as well as in CCK-PZ-induced enzyme secretion. The release of insulin, both basal and stimulated, was also significantly decreased by somatostatin.