Prostaglandin E1 was administered intravenously to 10 patients who had the adult respiratory distress syndrome associated with severe infection in order to investigate its hemodynamic effects. Infusion of PGE1 significantly decreased the mean pulmonary arterial pressure, mean systemic arterial pressure, pulmonary vascular resistance and systemic vascular resistance, and increased the cardiac index, oxygen delivery and oxygen consumption. No significant difference was noted in the intrapulmonary shunt fraction. These results indicate that administration of PGE1 improves pulmonary hemodynamics and tissue oxygenation in patients with acute respiratory distress syndrome, by reducing right ventricular afterload and increasing the cardiac index.