We have analyzed features of patients who had what appeared initially to be a minor head injury but who developed an acute traumatic intracranial hematoma. Over a 10-year period, 183 patients who were able to open their eyes spontaneously, were oriented to person, place, and time, and who obeyed commands when they were first seen at a hospital subsequently underwent operation for an acute intracranial hematoma. The hematoma was extradural in 54% of these patients. A history of altered consciousness or symptoms of headache and vomiting were present in 61% of the patients; 33% had a focal neurological deficit, and 43% had either focal deficit or signs of a basal skull fracture. A skull fracture was shown radiologically in 60% of patients, including 52% of those not clinically suspected of having an intracranial lesion. Six months after injury, 77% of the patients had made a moderate or good recovery. The possibility that a patient who has recently sustained a head injury might develop an acute intracranial hematoma can never be completely discounted, even when there are no abnormal clinical signs, and a skull x-ray retains a useful place in the investigation of selected patients with a minor head injury.