The evaluation and management of patients with minor head injury (MHI: history of loss of consciousness or posttraumatic amnesia and a GCS score >12) remain controversial. Recommendations vary from routine admission without computed tomographic (CT) scanning to mandatory CT scanning and admission to CT scanning without admission for selected patients. Previous reports examining this issue have included patients with associated non-CNS injuries who confound the interpretation of the data and affect outcome. We hypothesized that patients with MHI and no other reason for admission with normal neurologic examinations and normal CT scans would have a negligible risk of neurologic deterioration requiring surgical intervention. To validate this hypothesis we studied 2766 patients with an isolated MHI admitted to seven trauma centers between January 1, 1988, and December 31, 1991. There were 1898 male patients and 868 female patients; injury was blunt in 99%. A neurologic examination and a CT scan were performed on 2166 patients; 933 patients had normal neurologic examinations and normal CT scans and none required craniotomy; 1170 patients had normal CT scans and none required craniotomy; 2112 patients had normal neurologic examinations and 59 required craniotomy. The sensitivity of the CT scan was 100%, with positive predictive value of 10%, negative predictive value of 100%, and specificity of 51%. The use of CT alone as a diagnostic modality would have saved 3924 hospital days, including 814 ICU days, and $1,509,012 in hospital charges. Based on these data, we believe that CT scanning is essential in the management of patients with MHI and that if the neurologic examination is normal and the scan is negative patients can be safely discharged from the emergency room.