Somatostatin, a 28-amino-acid inhibitory polypeptide has been advocated for the treatment of upper gastrointestinal bleeding and acute pancreatitis. This study examines the effect of somatostatin in acute hemorrhagic pancreatitis in piglets (n = 12), weighing 8-12 kg. Six animals served as controls, and received only fluid resuscitation (0.9%, NaCl, 20 ml/kg/h). Six animals received somatostatin treatment consisting of a 15 micrograms/kg bolus i.v. given simultaneously with the induction of pancreatitis, and treatment continued with an intravenous infusion (15 micrograms/kg/h) for 5 h. Cardiac output, heart rate, blood pressure, arterial pO2, hematocrit and serum amylase were recorded before and each hour during the experiment. Regional blood flow in the gastrointestinal area was measured using the microsphere method. The microspheres labelled with three different isotopes were administered before the experiment and at 2 and 5 h, respectively. There was a significant decrease in the cardiac output (p less than 0.05) and an increase in systemic blood pressure in the somatostatin-treated group (p less than 0.025). Pancreatic blood flow decreased by 43% following somatostatin infusion. The decreases at 2 and 5 h were highly significant (p less than 0.005). Blood flow to the mucosal but not muscular region of the stomach was decreased by somatostatin. This study suggests that somatostatin might be harmful in acute pancreatitis due to its adverse effects on pancreatic blood flow and cardiac output. However, somatostatin may be effective in reducing gastrointestinal bleeding. If the drug is used clinically, careful monitoring of the cardiac output is necessary.