In anesthetized piglets the influence of an LD100 of Escherichia coli endotoxin (0.5 mg/kg IV, bolus injection) on several hemodynamic parameters and on survival time was studied. Endotoxin provoked a pronounced decrease in arterial pressure and cardiac output and an increase in portal venous and pulmonary arterial pressure and heart rate. Total peripheral and mesenteric vascular resistances displayed an initial increase followed by a sustained decrease, whereas pulmonary vascular resistance revealed a pronounced biphasic increase. All pigs died within 210 min following endotoxin administration. Pretreatment with the 5-HT2-antagonists R 41468 and R 50970 and with the prostanoid-synthesis inhibitor flurbiprofen induced a significant attenuation of the increase in pulmonary vascular resistance and beneficial effects on survival. Best survival results were obtained with prednisolone sodium succinate, although these results can only partly be ascribed to beneficial hemodynamic effects. The experiments with the opiate antagonists, however, point to detrimental effects.