The renal extraction of insulin and glucagon was studied in dogs subjected to temporary interruption of vascular perfusion of the liver. This was performed using hepatic artery occlusion after functional end-to-side portacaval anastomosis. The renal extraction of immunoreactive insulin and glucagon was studied by means of renal arterial-venous concentration differences with concurrent estimates of renal plasma flow and glomerular filtration rate. The degree of liver damage was reflected by dramatic increases of liver enzymes in the plasma after ischaemia and by hypoglycemia which developed in all the animals. Ninety minute occlusion of hepatic blood flow resulted in a dramatic reduction of renal plasma flow and glomerular filtration rate. Portacaval shunt alone had little effect on these parameters. Because hypoglycemia developed after hepatic insult, some animals were made hyperglycemic by intravenous infusion of glucose. In both (hypo- and hyperglycemic) groups of animals the percentage extraction of hormones by the kidney fell dramatically 60 minutes after the end of the hepatic ischaemia and this reduction persisted 180 min later. These data suggest that the impaired renal function may contribute to the increased plasma levels of islet hormones observed during acute hepatic failure.