Ischemic cerebrovascular disease accounts for more than 85% of all clinical stroke events with the remainder divided approximately equally between intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SH). The diagnosis of stroke requires differentiation from other diseases of the brain of acute onset based on clinical history, neurologic exam, and brain imaging. At least two-thirds of ischemic strokes result from atherothrombotic occlusive disease while embolism from a documented cardiac source and infarction of undetermined cause constitute the balance. Strokes resulting from hemorrhage, intraparenchymatous and subarachnoid, are fatal in about half the cases and hemorrhage survivors often have severe permanent disability. A number of key risk factors for stroke have been identified and their impact estimated. Hypertension is the principal risk factor for ischemic stroke with risk rising in proportion to level of blood pressure, systolic as well as diastolic.