The occurrence of hyperglycemia and glucosuria was investigated in urethane anesthetized rats. The substance found in urine was chromatographically identified with d-glucose. Marked increase in the arterial blood catecholamine concentration was observed. Hyperglycemia appeared after infusion of catecholamines in concentration comparable to that found in the blood of anaesthetized rats. The results support a hypothesis that the urethane-induced hyperglycemia is caused by an endogenous adrenaline liberation. Some observations in hypophysectomized and adrenalectomized rats indicate that the adrenal steroids may play a role in this reaction.