A higher prevalence of stroke is found in the patient with both diagnosed and undiagnosed diabetes and glucose intolerance. Because of local cerebral acidosis caused by ischemia and hyperglycemia, morbidity and mortality from a stroke are increased. Most studies show that individuals with admission serum glucose >120 mg/dl (6.7 mM) have a higher morbidity and mortality from a stroke. The prevalence of cerebral infarcts, especially lacunar infarcts, is increased and the prevalence of subarachnoid hemorrhage, cerebral hemorrhage, and transient ischemie attacks are decreased in the diabetic patient. Age, race, hypertension, and the presence of diabetic nephropathy and coronary and peripheral vascular disease are risk factors for stroke in the diabetic patient, whereas obesity, smoking, hyperlipidemia, and glycemie control are not. Investigation and treatment of the diabetic patient with a stroke is discussed.