The authors review 47 patients with closed-head injuries requiring treatment for acute subdural hematoma and report that 21 (45%) survived for 5 days or more. Follow-up study of these 21 survivors led to the following observations: that clinical evaluation of these patients is the most reliable index of their postoperative progress; that the diagnostic usefulness of postoperative cerebral arteriograms is limited because immediate postoperative changes tend to persist; that craniotomy is preferable to burr holes for removal of an acute hematoma; and that the value of cisternography, unless done serially, is limited since posttraumatic hydrocephalus develops rapidly and may persist indefinitely.