During two 12-month periods, 12,395 accident and emergency department attenders with head injury were collected. Those characteristics which were significantly more common in head-injured patients who had skull fractures on X-ray were identified. These characteristics were: recent alcohol consumption in adults, initial unconsciousness, amnesia of any duration, vomiting, neurological signs, injuries sustained by pedestrians, motorcyclists and cyclists. Such characteristics were then further examined and their power as diagnostic tests for the presence of skull fracture on X-ray was detailed. In individual patients and especially in children, these characteristics were generally of little value in identifying patients with fractures. It was considered that, in the majority of individual patients with head injuries, accurate clinical diagnosis of radiologically apparent fractures was not possible. In view of this and in the light of the known risks in patients with fractures, it was concluded that skull X-rays should continue to be used relatively freely in the management of these patients.