Glucagon, the polypeptide humoral substance produced mainly by the alpha cells of the pancreas, is generally considered as a metabolic hormone. Its influence on carbohydrate metabolism has been widely studied and is fairly well known. In addition to the glycogenolytic action, glucagon has also been found to have an inhibitory effect on gastrointestinal motility1-3 and gastric acid secretion.4,5 By which mechanisms these actions are produced by glucagon and if they are of any physiological significance is not known. The effect of glucagon on the cardiovascular system has been subject to much less study. In 1959, Shoemaker et al,6 using sulfobromophthalein (Bromsulphalein [BSP]) methods, studied the effect of glucagon on hepatic blood flow in dogs. They found an increase of blood flow which coincided with the serum glucose increase. In 1962, Merrill et al7 reported the effect of glucagon on the superior mesenteric vascular bed. In their