Objective: To reveal brain electrophysiological features by monitoring of AEEG before and after intracranial mass lesion surgery. Methods: In 260 patients with intracranial mass lesions

AEEG was serially recorded during 1~3 days before surgery as well as 1 week and 1-3 months after surgery. Results: (1) AEEG showed the abnormality rate of 88.1% before surgery

but the abnormality rate of AEEG were 97.7% and 77.7% during 1 week and 1~3 months after surgery. (2) 17 patients without symptomatic seizure before surgery developed symptomatic seizures after surgery

which suggests that cortex injury during surgery might increase an incidence of epilepsy. Conclusion: AEEG in monitoring the patients with encephalic space-occupying lesion before and after operation make it possible to observe the variations of brain function in time and it is helpful to clinical treatment.