The therapeutic window with the neuroprotectant nicotinamide (NAm) was tested in a model of stroke. Either 2, 4 or 6 h after the onset of transient (2 h) focal cerebral ischemia, Wistar rats received either saline or NAm (500 mg/kg). Sensory and motor behavioral scores and weight of the animals were obtained before surgery, and 2 h, 3 and 7 days after stroke onset. Cerebral infarct volumes were measured on day 7 after sacrifice. NAm given 4 or 6 h after stroke onset significantly (p<0.05) reduced the cerebral infarction and improved the behavioral scores, respectively, compared to saline-injected animals. There was a non-significant improvement in weight gained by NAm-treated rats at 3 and 7 days following stroke compared to the saline-injected controls.