Exogeneous endotoxaemia caused vasoconstriction of the juxtaglomerular arteries in otherwise healthy minipigs. This supports the view that reduced renal cortical blood flow in patients with liver disease can be caused by endotoxin. After portocaval anastomosis the efficacy of the liver RES to clear endotoxin was decreased due to the haemodynamic disorder. Thus, a dose of endotoxin, which was sublethal to healthy animals, became lethal owing to decreased RES-function. The increased endotoxin toxicity leads to a Shwartzman-Sanarelli-reaction. A dose of toxin which caused death in all animals with a portocaval shunt alone was not lethel in any animal in which an arterialization procedure was simultaneously performed, suggesting a possible improvement of RES function. These findings are of clinical importance for patients with renal failure in liver cirrhosis and hepatic failure. They suggest that endotoxaemia is of pathogenetic relevance in the development of functional renal failure.