Factors affecting prognosis of coma following various brain damages were studied on 567 patients who were “unconscious” upon admission to the Trauma Intensive Care Unit of Osaka University Hospital. The total consisted of 313 head injuries, 83 cerebrovascular diseases, 143 carbon monoxide poisonings and 28 post cardiac arrests. Time courses of recovery from unconsciousness were compared from the etiology of brain lesions. And then, in the head-injured patients, age and neurological signs and cerebral metabolic parameters in acute stage were investigated in relation to their outcomes. The conclusions are as follows: 1) Some differences in recovery rates of unconsciousness were observed from the nature of lesions. No recovery after one week's unconsciousness was noted in cases of both cardiac arrest and carbon monoxide poisoning patients. On the other hand, some patients with head injuries or cerebrovascular diseases regained consciousness even after one month of coma. 2) While pupillary abnormalities and decerebrate rigidity in adult patients following head injury promise prolonged unconsciousness or subsequent brain death, they do not always indicate fatal outcome or permanent disability in younger patients. 3) Long lasting decerebrate rigidity and hypocarbia are clues to “vegetative” survival. 4) CSF acidosis and jugular hyperoxia in acute stage are poor prognostic signs.