We conducted a multicenter, prospective study of head-injured patients to identify high-yield clinical criteria for acute intracranial injuries. Emergency patients with a history of blunt head trauma occurring within 2 weeks and who underwent nonenhanced cranial computed tomography (CT) were entered onto the study during a 12-month period. Of the 264 patients, 32 (12%) had abnormal CT findings. Nine high-yield variables were associated with abnormal CT findings: alcohol use before injury, antegrade amnesia, prolonged loss of consciousness, anisocoria and/or fixed and dilated pupils, abnormal Babinski reflex, focal motor paralysis, cranial nerve deficit, Glasgow coma scale score of less than 15, and clinical signs of basilar skull fracture. Patients 2 years old or younger or older than 60 years of age showed a significantly greater prevalence of abnormal CT findings than patients of other ages.