Objective To investigate the relationship between the serum concentration of neuron-specific enolase (NSE) and the brain damage severity and the prognosis of acute head injuried patients. Methods Early serum levels of NSE were measured in 70 patients with acute head injury by radioimmunoassay. The concentration of NSE was analysed by combining with GCS and GOS systems. Results NSE levels in serum of patients with major(a), minor(b) head injuries and control individuals(c) were (25 78 ? 10 80)ng/ml, (19 58 ? 8 91)ng/ml and (9 51 ? 2 79)ng/ml respectively, differences of which were significant (P a-b