A retrospective review of 373 adult patients admitted to Harbor General Hospital between 1980 and 1984 for minor closed head injury (Glasgow coma scale 13-15) was performed to determine the benefits of skull radiography, computed tomographic (CT) scanning of the head, and admission for observation. Variables reviewed were mental status, neurological examination, presence or absence of loss of consciousness, clinical evidence of basilar skull fracture, and fracture on skull radiography. The neurological examination (including mental status and Glasgow coma scale) in the emergency room was the best predictor of subsequent deterioration or the presence of an operative hematoma. The only patients with Glasgow coma scale scores of 15 who required surgical evacuation of an extraaxial hematoma had focal neurological deficits referable to hemispheric compression, with or without an abnormal mental status. A Glasgow coma scale score of 13 or 14 places the patient at risk either of having a hematoma requiring surgery or of deteriorating. We recommend that a head CT scan be obtained on all patients with Glasgow coma scale scores of less than 15, abnormal mental status, or hemispheric neurological deficits. If no operative lesion is found on the CT scan, the patient should be admitted for observation because there is still a risk of deterioration. Those with a Glasgow coma scale score of 15, a normal mental status, and no hemispheric neurological deficit may be discharged to be observed at home by a competent observer despite basilar or calvarial skull fracture, loss of consciousness, or cranial nerve deficit. No benefit was gained from skull radiography in any group.