A consecutive series of 107 comatose patients with head injury was studied with regard to the proper role of serial computerized tomography for clinical management and as a research tool for studying the pathophysiology of severe head trauma. In this prospective study patients had serial CT scans on days 1, 3, 5, 7, 14, at 3 months, and at 1 year (day 1 is the day of admission). In seven instances CT scanning was responsible for detection of late intracranial lesions requiring surgical decompression two weeks to one year after injury. No surgically significant lesions were, however, detected by routine scanning on the pre-determined days in the early post-trauma period that had not already been signalled by changes in the neurological status, intracranial pressure, or volume pressure response. It is concluded that for purposes of clinical management, additional scans should be obtained in the following circumstances: 1) 1 day post-craniotomy, 2) no improvement by day 3, 3) at 2-3 weeks, and 4) at 3 months. All other scans should be obtained as needed. As a research tool, serial CT scanning is of value in studying post-traumatic hydrocephalus, delayed intracerebral hematomas, and intraventricular hemorrhage.