This study aimed at determining the release and action of insulin in liver cirrhosis. Eight non-diabetic patients with alcoholic liver cirrhosis and eight age-, sex-, and weight-matched controls were investigated. The clearance and hypoglycemic action of insulin were determined after a brief intravenous infusion of insulin (10 mU/kg). Glucose tolerance and insulin response were determined after rapid intravenous infusion of 25 g glucose. In the cirrhotic patients the decrease in glucose tolerance was associated with a) an unchanged insulin clearance, b) a decreased hypoglycemic action of insulin, and c) a marked impairment in the early insulin response and a slight, but not significant, increase in the late insulin response. In the cirrhotic group glucose tolerance varied with the early (and late) insulin response and with the hypoglycemic action of insulin. It is concluded that both insulin action and the early insulin response are impaired in alcoholic liver cirrhosis and that deterioration of the early insulin release plays an important role for deterioration of glucose tolerance.