It has recently been claimed that an increase in creatine kinase isoenzyme BB(CK‐BB) in cerebrospinal fluid (CSF) is well correlated with the cerebral outcome in patients resuscitated after cardiac arrest. Twentyone such patients consecutively admitted from outside this hospital participated in the study. The patients were divided into two groups: 6 survivors and 15 nonsurvivors. The median CSF‐CK‐BB value was 5 U/L among nonsurvivors and below detection limit among survivors (NS). However, the predictive value of a positive test is limited, since only 6 of 15 nonsurvivors (40%) had an increase in CSF‐CK‐BB (predictive value of positive test=67%). The predictive value of a negative test is limited, since 3 of 6 survivors (50%) showed no rise in CSF‐CK‐BB (predictive value of negative test=25%). No relationship between cerebral dysfunction and CSF‐CK‐BB values was revealed. Thus, CSF‐CK‐BB does not predict the clinical outcome in patients resuscitated after cardiac arrest.