A small number of patients with an apparently minor head injury will develop a life-threatening intracranial hematoma that must be rapidly detected and removed. To assess the risk of a significant intracranial neurosurgical complication after apparently minor head injury, the authors collected data prospectively on 610 patients who had sustained a transient posttraumatic loss of consciousness or other neurological function and who had a Glasgow Coma Scale (GCS) score of 13, 14, or 15 in the emergency room. Skull x-ray films were obtained in 583 patients, 66 of whom (10.8% of the study population) had cranial fractures. Eighteen of the 610 patients (3.0%) required a neurosurgical procedure. Three acute subdural hematomas, one epidural hematoma, and one traumatic intracerebral hematoma required craniotomy. Of the 66 patients who had skull fracture, 7.6% required a craniotomy for intracranial hematoma. Thirteen (19.7%) of the 66 patients with skull fracture required an operative procedure as compared to five (1.0%) of the 517 patients without skull fracture. Two patients with a normal GCS score of 15 and normal skull x-ray films subsequently underwent operative treatment. The cost of three alternative management schemes for these patients was estimated. A 50% reduction in cost of management could be effects by the use of computerized tomography (CT) scans (or possibly skull x-ray films) in determining which of the patients who are alert at the time of presentation should be admitted for observation. Several other conclusions can be drawn from this study. First, an initial GCS score between 13 and 15 does not necessarily indicate that a patient has sustained a trivial head injury, since 3% of such patients will require an operative procedure despite an initially normal level of alertness. Second, an abnormal skull x-ray film increases by a factor of 20 the probability that a patient will need neurosurgical treatment. Third, it is very unusual for patients who have a GCS score of 15 and a normal skull x-ray film to have a significant neurosurgical complication. Fourth, the alternative management schemes that depend on selective use of skull films and CT scans may significantly reduce the cost of caring for patients with minor head injury.