The aim of this study was to examine whether an increase in the serum concentrations of the two brain enzymes creatine kinase BB (CK-BB) and neuron specific enolase (NSE) can be demonstrated in patients with acute head injury and whether such an increase reflects release from damaged brain tissue. In 60 patients who had suffered minor to severe head injury, serial blood samples were drawn during the first hours after impact, and CK-BB and NSE were measured by radioimmunoassay. Computed tomography (CT) was also performed shortly after admission to hospital, and was repeated 1-3 days later in selected patients. Increased serum concentrations of both CK-BB and NSE were found in 88% of the patients with moderate to severe head injury (group 1, n = 18) and in 23% of the patients with minor head injury (group 2, n = 42), whereas CT showed contusion in only 41% and 2% of the group 1 and 2 patients, respectively. The following findings suggest that the enzymes had been released from brain tissue: 1) The maximum concentrations of CK-BB and NSE correlated with the severity of injury as assessed clinically and with the volume of contusion as estimated from CT (r = 0.79 with CK-BB, r = 0.72 with NSE). 2) The maximum concentrations of CK-BB and NSE were closely correlated (r = 0.87).(ABSTRACT TRUNCATED AT 250 WORDS)