The aim of the present prospective work was to study the etiologic diagnosis and prognosis of the comatose patients for whom a neurologic examination is requested. It included 148 consecutive cases admitted to the emergency room of a general hospital. Coma was caused by supratentorial lesions in 38%, subtentorial lesions in 10%, diffuse or metabolic brain dysfunction in 49%, and psychiatric disorder in 1% of the patients. CT scan was the most valuable ancillary exam, modifying the initial etiologic diagnosis in 42% of the cases on whom it was performed. Seventy percent of the patients died. Coma caused by structural lesions had a worse outcome than coma caused by diffuse or metabolic brain dysfunction (intoxications excluded), and this type of coma had a worse outcome than drug-induced coma. The presence of anisocoria, the number of brainstem reflexes present and the pattern of motor response, as well as the Glasgow Coma Scale score, predicted the outcome.