Defects in insulin secretion and/or action contribute to the hyperglycemia of stressed and diabetic patients, we hypothesize failure to suppress glucagon also plays a role. We examined the chronic impact of glucagon on glucose uptake in chronically catheterized conscious depancreatized dogs placed on 5 days of nutritional support (NS). For 3 days of NS a variable intraportal infusion of insulin was given to maintain isoglycemia (~120 mg/dl). On day3 of NS animals received a constant low infusion of insulin (0.4 mU/kg/min) and either no glucagon (CONT), basal glucagon (0.7 ng/kg/min; BasG) or elevated glucagon (2.4 ng/kg/min; HiG) for the remaining 2 days. Glucose in NS was varied to maintain isoglycemia. An additional group (HiG+I) received elevated insulin (1 mU/kg/min) to maintain glucose requirements in the presence of elevated glucagon. On day 5 of NS hepatic substrate balance was assessed. Insulin and glucagon levels were 10±2, 9±1, 7±1, 24±4 µU/ml, and 24±5, 39±3, 80±11, 79±5 pg/ml, CONT, BasG, HiG, and HiG+I respectively. Glucagon infusion decreased the glucose requirements (9.3±0.1, 4.6±1.2, 0.9±0.4 and 11.3±1.0 mg/kg/min). Glucose uptake by both hepatic (5.1±0.4, 1.7±0.9, -1.0±0.4 and 1.2±0.4 mg/kg/min) and non hepatic (4.2±0.3, 2.9±0.7, 1.9±0.3 and 10.2± 1.0 mg/kg/min) tissues decreased. Additional insulin augmented non-hepatic glucose uptake and only partially improved hepatic glucose uptake. In summary, glucagon impaired hepatic and non-hepatic glucose uptake. Compensatory hyperinsulinemia restored non-hepatic glucose uptake and partially corrected hepatic metabolism. Thus, persistent inappropriate secretion of glucagon likely contributes to the insulin resistance and glucose intolerance observed in obese and diabetic individuals.