The neuroprotective activity of the plant Lepidium meyenii (Maca) was studied in two experimental models: in vitro and in vivo. Crayfish neurons were pretreated with vehicle or the pentane extract from Maca, subjected to H(2)O(2), and their viability determined microscopically and chemically. A significant concentration-neuroprotective effect relationship was demonstrated. The pentane extract was then administered intravenously to rats prior to and following middle cerebral artery occlusion. While infarct volumes were decreased for the lower dose, higher doses increased infarct volumes compared to controls. These results suggest a potential application of Maca as a neuroprotectant.