Objective To investigate the relationship between the extent of the damage in traumatic brain injury(TBI)and S-100B protein levels in serum and cerebrospinal fluid (CSF).Methods 45 cases of TBI patients were classified into three cohorts according to the Glasgow Coma Scale (GCS):minor grade,moderate and severe(case group), S-100B protein levels in serum and CSF were measured with ELISA in these patients 1,3,5,7 days after the injury, and selected 20 cases in control group including operative patients with hernia or varicose vein and healthy volunteers, analyzed the relationship between S-100B levels in serum and CSF and the degree of TBI damage.Results Case groups have a significantly higher serum, CSF S-100B levels than control group (P<0.01;P<0.01);GCS in patients were negatively correlated with serum and CSF S-100B levels(r=-0.893,P<0.01;r=-0.947, P<0.01);Differences of S-100B levels in serum and CSF among minor grade,moderate and severe being significant (P<0.01);Positive correlation was found between S-100B levels in serum and in CSF in case groups;Conclusions S-100B assay in serum and CSF can indicate the extent of lesion of TBI both,but with various characteristics.