The present study was undertaken to determine the role of glucagon in determining the disposition of an oral glucose load in normal man. To accomplish this, the plasma glucose response to an oral glucose load was determined in four normal men who were studied on two occasions. During one study, glucagon (3 ng/kg.min) was administered to prevent the fall in plasma glucagon noted after oral glucose ingestion. Despite elevation of plasma glucagon levels to 350 pg/ml in this protocol, the plasma insulin and glucose levels achieved were virtually identical to those obtained after oral glucose alone. These results indicate that neither physiological elevations of plasma glucagon nor the suppression of plasma glucagon seen during oral glucose administration alter glucose tolerance in normal man. Thus, in a normal man capable of secreting appropriate amounts of insulin in response to the ingestion of glucose, glucagon plays no appreciable role in the disposition of this glucose load.