The effect of low dose infusions of somatostatin on meal stimulated gastric acid secretion was studied in eight healthy volunteers by intragastric titration after a peptone test meal with radioimmunoassay control of the plasma concentrations of somatostatin and the pancreatic hormones glucagon and insulin. Infusion of somatostatin in a dose of 100 ng/kg/h, resulting in a plasma concentration of 13.4 +/- 2.1 pmol/l, inhibited acid secretion significantly, and in a dose of 800 ng/kg/h, with corresponding plasma concentration of 66.5 +/- 12.0 pmol/l the acid secretion was virtually abolished. Plasma concentrations of insulin and pancreatic glucagon decreased significantly during infusion of 200 ng/kg/h (24.5 +/- 7.5 pmol/l) and glucose concentrations increased. Serum gastrin was only significantly decreased during the highest dose of somatostatin. The range of plasma somatostatin concentrations obtained with the lower doses correspond to reported physiological variations. The results support the concept that somatostatin participates in the hormonal control of the pancreatic endocrine and the acid secretion.