The effects of somatostatin on hepatic and systemic hemodynamics were investigated in 17 patients with chronic liver disease and severe portal hypertension during the hemodynamic assessment before elective portal-systemic shunt surgery. The injection of somatostatin (1.0 microgram/kg) caused a decrease of the wedged hepatic venous pressure, from 19.5 +/- SE 1.3 mmHg to 14.0 +/- 1.0 mmHg (p < 0.001). Injections of 0.5 and 2.0 microgram/kg had similar effects. During somatostatin infusion at a constant rate (7.5 microgram/min) there was a reduction of the wedged hepatic venous pressure (-17.0%, p < 0.001) and estimated hepatic blood flow (-17.5%, p < 0.01) but no significant changes in hepatic vascular resistance, cardiac output, systemic blood pressure, peripheral resistance, or cardiopulmonary pressures. In marked contrast to the selective action of somatostatin on splanchnic hemodynamics, vasopressin infusion (0.3 U/min) in 6 patients caused not only significant falls in the wedged hepatic venous pressure and estimated hepatic blood flow (-28.6% and -31.8%, respectively), but also significant changes in the systemic circulation, including a reduction of the cardiac output (-19.7%, p < 0.01) and heart rate (-12.6%, p < 0.01) and an increase of the arterial pressure (+18.8%, p < 0.01) and peripheral resistance (+46.8%, p < 0.01). These results show that somatostatin effectively reduces hepatic blood flow and portal pressure in patients with cirrhosis and severe portal hypertension, without altering the systemic circulation.