To investigate the possibility of improving the accuracy of prognostication in early hypoxic brain damage, 12 patients with global cerebral ischemia (GCI) due to circulatory arrest outside hospital were followed until death or for 1 yr. Five who survived for more than 2 weeks displayed better values on coma scoring from 16 h-3 days, compared to those who succumbed within 2 weeks. In 2 week-survivors, lumbar puncture revealed consistently lower adenylate kinase (AK) activity in cerebrospinal fluid (CSF) at 24 h than in the other patients, whereas glutathione and lactate values overlapped to some degree. The CSF-AK activity at 48–72 h was less correlated to clinical outcome. It is concluded that the results from coma scoring, based upon clinical observation, and from determination of AK activity in CSF at 24 h reinforce each other in discriminative power to predict prognosis in these patients.