Intracerebral hematoma was experimentally produced by injection of arterial auto-blood into the area of the internal capsule with stereotaximetry in dogs. Forty-eight hours after injection of blood the hematoma was aspirated, the aspirated and the non-aspirated cases were followed electroencephalographically. EEG recording showed localized or generalized slow wave activity immediately after the intracerebral blood injection, which continued even after two months in non-aspirated cases. Marked decrease of the slow activity was observed shortly after aspiration and EEG returned to almost normal pattern after one week. According to the results, it was made clear that the exstirpation of blood clot was effective of the prevention of functional disturbance of nerve cells caused by intracerebral hematoma.