Effects of YM737[N-(N-r-L-glutamyl-L-cysteinyl)glycine 1-isopropyl ester sulfate monohydrate], a new glutathione (GSH) analog more readily transported into cells than GSH, on cerebral ischemia were compared with those of GSH and some other drugs in rats subjected to occlusion of the bilateral carotid arteries. YM737 significantly reduced lethality, increased brain-water levels as measured by both dry-wet and NMR methods, and increased malondialdehyde (MDA) levels in the cerebral ischemic rats. On the other hand, pharmacological actions of GSH itself was less than those of YM737. In the ischemic rats used in the present study, there was no significant difference in 31P-NMR signals between the normal and the cerebral ischemic rats. These results suggest that YM737 showed anti-cerebral ischemic effects presumably due, in part, to inhibition of lipid peroxidative responses.