Plasma glucose and glucagon concentrations were measured in the portal vein of six healthy, anaesthetized pigs submitted to an intravenous arginine infusion test. A monophasic glucagon response was observed in all pigs, the peak glucagon value being reached within an average of 5 minutes after the beginning of the infusion. The glucagon response, expressed as the incremental area below the hormone concentration curve, correlated inversely with the plasma glucose concentration before the start of arginine infusion (r=0.78) (p less than 0.05) indicating that glucose is a potent inhibitor of arginine-induced glucagon secretion in pigs.