The blood glucose concentration is the resultant of a dynamic equilibrium between the amount of glucose taken up by the tissues and that supplied to the blood by the liver. Under ordinary circumstances this concentration is maintained with relative constancy in the healthy individual, but fluctuates much more widely in the person with diabetes mellitus. In all individuals the ingestion of carbohydrate food tends to raise the blood glucose level, and physical exercise tends to depress it. The administration of the hormones which are concerned with the regulation of carbohydrate metabolism (such as epinephrine, insulin, adrenal cortical steroids, and pituitary growth hormone) may also cause changes in the circulating glucose. Physical stresses such as infections and trauma likewise affect the blood glucose regulation, apparently because they lead to the elaboration of these hormones as a part of the adaptive processes of the organism. The function of the endocrine glands which regulate carbohydrate metabolism may be altered also by stimuli arising in the external environment in the form of events or situations which are evaluated by the individual as threatening, and which therefore initiate adaptive responses mediated through the central nervous system. It has long been felt that stimuli of this sort might also lead to changes in the level of circulating glucose; and in fact experimental evidence has indicated that hyperglycemia can be produced in diabetic persons during psychiatric interviews. 1 The present study was undertaken in order to examine the effects of stressful events and situations upon the level of glucose in the circulating blood of diabetic and nondiabetic individuals.