We prospectively studied 712 consecutive patients during a 1-year period who presented with amnesia or loss of consciousness after nonpenetrating head trauma and who had a perfect Glasgow Coma Scale score of 15. Of the 67 (9.4%) patients with acute traumatic lesions disclosed by computed tomography (CT) of the head, 2 required neurosurgical intervention and 1 died. Four factors were statistically correlated (P < 0.05) with abnormal CT findings: Older age, white race, signs of basilar skull fracture, and being either a pedestrian hit by a motor vehicle or a victim of an assault. Sex, length of antero- or retrograde amnesia, forward and reverse digit spans, object recall, focal abnormality on the general neurological exam, and subjective complaints were not statistically correlated with CT abnormality. Using step-wise discriminant function analysis, no single item or combination of items could be used to classify 95% of the patients into either the normal or abnormal CT group. Therefore, regardless of age, mechanism of injury, or clinical findings, intracranial lesions cannot be completely excluded clinically on head-trauma patients who have loss of consciousness or amnesia, even if the Glasgow Coma Scale score is 15. However, only two patients (0.3%) required neurosurgical intervention.