This review summarizes evidence showing inhibition of insulin release by epinephrine and norepinephrine. The receptor theory for catecholamine action is discussed and the inhibition shown to be mediated by α-adrenergic receptor stimulation; β-adrenergic receptors are also described which stimulate insulin release, indicating a unique dual receptor system in the pancreatic islet. The possible physiologic importance of these findings is suggested in a discussion of the carbohydrate intolerance found in patients with pheochromocytoma and during severe hypothermia in children. A possible relation of the inhibition of insulin release and the increased fatty acid mobilization caused by catecholamines to exacerbations of the diabetic syndrome is examined. It is postulated that the catecholamine release which is stimulated by volume depletion, infection, or stress may be an important "reversible" factor in some patients with diabetic ketoacidosis.