Levels of brain creatine phosphokinase (CPK), glutamic oxalic transaminase, lactate dehydrogenase, and lactate in lumbar cerebrospinal fluid (CSF) were analyzed as an adjunctive study in a randomized clinical trial evaluating the effects of thiopental loading intravenously in comatose survivors of cardiac arrest. Three hospitals participated and a total of 62 cases of enzyme changes were studied. Enzyme levels but not lactate were higher at 48 hours than at 24 hours after restoration of spontaneous circulation. All enzymes were highly correlated with one another at 24 and 48 hours (P < .001). There was a significant negative correlation between cerebral recovery and increased CPK levels at 24 hours (P < .05), and a highly significant correlation with all three enzyme levels at 48 hours (P < .0001). The increase of cytosolic enzyme activity in lumbar CSF reflects permanent brain damage, and there is a relationship between activity levels and cerebral outcome.