Studies were carried out in rabbits to localize by electrical stimulation the sites in the hypothalamus that are concerned with the production of hyperglycemia, and to determine the contribution of the sympathetico-adrenal system in producing this effect. Stimulation of the anterior hypothalamic area, paraventricular nuclei, and rostral border of the ventromedial nuclei produced a significant elevation of blood glucose in normal rabbits and also in adrenal-demedullated animals. Corticotropin (ACTH), 2 U/kg, produced a hyperglycemia comparable to that observed following electrical stimulation, whereas growth hormone (GH), 2.5 mg/kg, had no effect on blood glucose. The data indicate that the anterior hypothalamus plays a part in the regulation of blood glucose, which is independent of the sympathico-adrenal system. It is suggested that the hyperglycemia produced by hypothalamic stimulation in these studies is due to the release of one or more anti-insulin factors by the anterior pituitary.