Abstract: Objective To evaluate the value of somatosensory evoked potential（SEP） during carotid endarterectomy in monitoring cerebral ischemia. Methods Seventy patients（63 males and 7 females） with a mean age of 65.6 years were included in this study.Their SEP was monitored.Unilatateral stricture was found in 53 patients and bilateral stricture was found in 17 patients,the stricture rate was over 70%.Tibial nerves were stimulated,SEP in bilateral cortex was recorded,and 50% reduction in P40 wave amplitude was used as the warning signal of cerebral ischemia. Results Types I,II,and III SEP wave forms were found in 44,23,and 3 patients,respectively,but type IV SEP was not found in any patients. Conclusion SEP monitoring can indicate the cerebral perfusion state after carotid endarterectomym and is an ideal method for monitoring cerebral blood perfusion.However,nerve dysfunction cannot be completely excluded only based on its negative results.