Recent scientific data suggest that there is a "window of opportunity" between the onset of brain ischemia and irreversible neuronal death. Although neurons can withstand complete absence of blood flow for only minutes, collateral circulation typically surrounds the "core" of the stroke. In these brain regions known as the ischemic penumbra, brain tissue can survive for several hours following stroke onset. Recent studies suggest that neuroprotective agents would give these viable neurons the chance for recovery. This article reviews the mechanisms of ischemic neuronal injury, mechanism of action of neuroprotective agents, current neuroprotective clinical trials, and guidelines for patient care management.