Object: Acori graminei rhizoma(AGR) extract is clinically used to treat the cerebral ischemia in Korea. The present study was undertaken to study the neuroprotective effect of AGR extract in middle cerebral artery occlusion(MCAO) rats. Methods: Changes of extracellular levels of glutamate, aspartate, GABA, glycine, taurine, tyrosine, alanine in striatum were collected at 20 minutes interval by in vivo microdialysis and then analyzed by HPLC(high performance liquid chromatography) in rats subjected to permanent focal cerebral ischemia induced by 2 hours of MCAO. AGR extract was orally administrated before MCAO. Different animals were used for measurement of cerebral infarction volume induced by 24 hours of MCAO with TTC staining and image analysis. Result : The infarction volume was decreased and focal cerebral ischemia - induced increase of extracellular glutamate, aspartate, and tyrosine were inhibited after the treatment of AGR extract. On the other hand, the increase of glycine and alanine not but GABA and taurine were enhenced after the treatment of AGR extract. Conclusion: These results suggest that AGR extract can playa role in protecting against cerebral ischemia by regulating extracellular levels of excitatory and inhibitory amino acid neurotransmitters.