Pancreatic glucagon and insulin secretion in response to glucose injection and infusion were examined in 7 obese subjects with normal, 5 with borderline and 11 with impaired carbohydrate tolerances, and also in 19 non-obese healthy controls. All obese subjects exhibited significant hyperinsulinemia during the later phase of secretion. Early insulin response was significantly reduced in the obese with carbohydrate intolerance. No significant differences in fasting glucagon levels were observed between controls and all 3 obese groups; glucagon response to glucose was also comparable in all groups, regardless of degree of carbohydrate tolerance. This finding suggests that there is no alpha-cell resistance to glucose suppression in obesity. The increased insulin:glucagon ratio seen in all obese subjects during glucose infusion reflects a state of relative anabolism. Glucagon secretion was not associated with body weight, glucose tolerance or insulin response.