We reviewed the records of 1538 mild head injury patients admitted during a 4 1/2-year period to the Southern New Jersey Regional Trauma Center. All patients had experienced brief loss of consciousness or amnesia, but had a normal or near normal neurologic examination on admission, with Glasgow Coma Scale (GCS) scores of 13-15 and no focal neurologic deficit. Routine urgent cranial CT scans were obtained on all patients, and correlations between skull fractures and intracranial lesions investigated. Two hundred sixty-five patients (17.2%) harbored 340 lesions on CT scans, of which 131 were fractures and 209 were intracranial abnormalities. Fifty-eight patients needed surgery for their intracranial lesions; 23 of them had no skull fractures. None of the 1339 patients without CT evidence of intracranial lesions deteriorated under observation. We conclude that clinical observation with or without skull x-ray films is inadequate to rule out potentially dangerous intracranial lesions in apparently mild head injuries. If there is a history of loss of consciousness or amnesia, an immediate CT scan is indicated. If the results of the CT scan are normal and there are no other indications for admission, these patients may be safely discharged.