On the grounds of studies carried out in the last ten years, the authors criticize the usual classification of comas and question the Glasgow scale (opening of eyes, verbal answer, motor response). Their description of brain stem injury by axial herniation and explanation of the role of diffuse encephalic lesions causing intracranial hypertension is based upon anatomo-clinical findings and results of investigations in comatose patients with head injury. For prognostic purposes, a simple and fairly reliable classification of post-traumatic comas is proposed. Comas are divided into five stages of rostro-caudal destructuration (cortico-sub-cortical, diencephalic, meso-diencephalic, mesencephalic and pontic) by studying the response to pain (unadapted, adapted, absent) and four brain stem reflexes (fronto-orbicular, vertical and horizontal oculocephalic, light reflexes).