The aim of this study was to determine cerebrospinal fluid (CSF) and serum neuron-specific enolase (NSE) concentrations in a normal population and to analyse their relationship with sex and age. The sample was recruited among patients undergoing spinal anaesthesia, without neurological diseases. NSE was determined by means of immunometric assay. One hundred and eight patients (68 men) were recruited. CSF-NSE concentration was (mean +/- SD) 17.3 +/- 4.6 ng/ml (men 17.4 +/- 4.2, women 17.0 +/- 5.2, P = 0.62); serum concentration was 8.7 +/- 3.9 ng/ml (men 8.9 +/- 3.9, women 8.3 +/- 4.0, P = 0.06). The mean CSF/serum NSE ratio was 2.3 +/- 0.8 (men 2.2 +/- 0.8, women 2.4 +/- 0.9, P = 0.22). In both sexes, simple regression analysis showed not significantly increasing concentrations with advancing age for both CSF and serum NSE. Serum and CSF concentrations did not correlate in both sexes. In our study, CSF-NSE was twice the serum concentration; both were not influenced by sex or age. Serum and CSF-NSE values vary widely among different studies on normal populations because of different determination methods; therefore, each laboratory should obtain its own reference values. Finally, serum NSE should be used with caution as an indicator of CSF concentration as no correlation could be demonstrated between them in our study.