Acute hypertensive response is the elevation of blood pressure above normal and premorbid values that initially occurs within the first 24 hours of symptom onset in patients with intracerebral hemorrhage (ICH). Hypertension is the most frequent and most important risk factor for ICH. Hypertensive patients suspected of primary intraparenchymal hematoma died and were subsequently autopsied in order to assess the alterations of extraparenchymal and intraparenchymal vascular structures. Stroke patients with a history of hypertension are at risk of critical hypoperfusion for mean arterial pressure levels usually well tolerated by normotensive individuals. Drugs recommended for use in lowering blood pressure in acute stroke include labetalol, hydralazine, nicardipine, and nitroprusside. The Antihypertensive Treatment in Acute Cerebral Hemorrhage (ATACH) trial is a prospective, open label phase I safety and tolerability study started in 2005 that plans to study 60 patients.