Neurological and pathological EEG findingsfollowing the carotid artery ligation were examinedon six cases of malignant cancer.In order to prevent the accidental rupture ofthe artery by cancerous invasion ligation was graduallymade during six days.No severe neurological signs wern seen but pathologicalEEG findings such as 1) focal delta waveand 30-40c/s range gamma wave activity 2) asymmetricalabnormality 3) alpha wave supression wereobserved.Possible intracranial complications and EEGfindings after blocking of the major cerebral arterywere discussed in view of previous studies and ourligation procedure was considered to be a suitablemethod.