Background and Purpose-Pretreatment with intraventricular brain-derived neurotrophic factor (BDNF) reduces ischemic damage after focal cerebral ischemia. In this experiment we studied the effect of intravenous BDNF delivered after focal cerebral ischemia on neurological outcome, infarct size, and expression of proapoptotic and antiapoptotic proteins Bax and Bcl-2, respectively. Methods-With the use of the suture occlusion technique, the right middle cerebral artery in rats was temporarily occluded for 2 hours. Thirty minutes after vessel occlusion, BDNF (300 g/kg per hour in vehicle; nϭ12) or vehicle alone (nϭ13) was continuously infused intravenously for 3 hours. After 24 hours the animals were weighed and neurologically assessed on a 5-point scale. The animals were then killed, and brains underwent either 2,3,5-triphenyltetrazolium chloride staining for assessment of infarct volume or paraffin embedding for morphology and immunohistochemistry (Bax, Bcl-2). Results-Physiological parameters (mean arterial blood pressure, PO 2 , PCO 2 , pH, body temperature, glucose) and weight revealed no difference between groups. Neurological deficit was improved in BDNF-treated animals versus controls (PϽ0.05, unpaired, 2-tailed t test). MeanϮSD infarct volume was 229.7Ϯ97.7 mm 3 in controls and 121.3Ϯ80.2 mm