Electrical stimulation of the lateral hypothalamus resulted in electrocardiographic evidence of acute myocardial ischemia in 35% of normal adult rats under anesthesia. Mean arterial blood pressure was also elevated. Study of vascular corrosion casts disclosed that spasm of smaller branches of the coronary circulation, rather than the major epicardial arteries, was the main cause of the ischemic response. The histologic changes of the same experimental treatment in a separate group of animals revealed multiple focal areas of tissue damage throughout the myocardium, which were quantitatively assessed. The results may be relevant for the clinical problem of various forms of ischemic heart disease in which little evidence is found for organic (atherosclerosis) or dynamic (spasm) stenosis involving the major coronary arteries.