The depth and duration of coma were important indicators of neurologic outcome after cardiac arrest in man. Response to painful stimuli, at first reflex and later purposeful, followed by gradual progression to wakefulness by 24 h, indicated a favorable prognosis. Persistent coma or arousal only to the level of reflex response to pain at 12 and 24 h carried a very high risk of death or severe neurologic damage. Absent oculovestibular responses at 12 h and presence of decorticate or decerebrate responses at 24 h or later were additional indexes of neurologic damage. If the initial examination showed not only coma and apnea but dilated pupils and absence of the major cephalic reflexes, then brain death may have occurred and EEG recording with repeat examinations at 12h or more is indicated.