The aim of this study was to observe cerebral and systemic oxygen extraction after human cardiac arrest with return of spontaneous circulation. Eight adult patients after non-traumatic, cardiac arrest were included. Cerebral and systemic oxygen extraction ratios were measured together with haemodynamic variables beginning 2 hours after cardiac arrest and every 4 hours thereafter until 24 hours. Between 2 and 12 hours after cardiac arrest cerebral oxygen extraction values ranged from very low over normal to very high. In the further course these values were reduced until 24 hours in six patients. Two patients who were still alive after 6 months, both severely mentally disabled, had a higher cerebral oxygen extraction ratios in comparison with non-survivors. Systemic oxygen extraction seemed to vary more than the cerebral oxygen extraction. The two long-term survivors had normal to supranormal values from 8 to 24 hours. In conclusion cerebral oxygen extraction was higher in long-term cardiac arrest survivors than in non-survivors between 12 and 24 hours after the event. Further, a better quality of neurological recovery was associated with higher cerebral oxygen extraction. Systemic oxygen extraction was also impaired, but to a lesser extent, especially in long-term survivors.