Circulating insulin was determined by radioimmunoassay in ten children with cirrhosis of the liver and in 6 age-matched controls. They were found to be elevated in cirrhotics during fasting as well as at 1/2, 1, 1 1/2 and 2 h during the oral glucose tolerance test. These determinations were also carried out in two children with extrahepatic portal hypertension to show the possible role of portal systemic shunts for the elevated serum insulin levels. We believe that the hyperinsulinemia of these patients was related to decreased insulin degradation by the liver as well as to portal-systemic shunting.