THE NONSURGICAL treatment of subdural hematoma has offered unique opportunities for the study of clinical-electroencephalographic correlations in the natural history of this condition. In unoperated cases serial clinical, radiographic, and EEG examinations may be carried out at long intervals, and previously unobtainable insights into the pathophysiology of subdural hematoma may be obtained. For many years the only method for establishing a diagnosis of subdural hematoma was the performance of burr-hole openings through the calvaria and direct visualization of the dura. The logical corollary of this diagnostic method was the evacuation of any fluid collection found to be present. The perfection and dissemination of techniques for percutaneous carotid angiography made it possible to diagnose the condition without surgery and undoubtedly resulted in the disclosure of many cases which would have otherwise gone unrecognized. In spite of these new developments, however, treatment methods conditioned by earlier experience have continued to prevail in