Concentrations of glial fibrillary acidic protein (GFAp) and light subunit neurofilament protein (NFL) in cerebrospinal fluid (CSF) were measured in patients with second-stage Trypanosoma brucei gambiense sleeping sickness. Correlations between GFAp and NFL in CSF as markers for astrogliosis and neurodegeneration, and clinical and biological data were investigated. Abnormal levels of GFAp and NFL were significantly associated with increasing CSF cell number and protein concentration, and with the absence of lymph nodes or the absence of trypanosomes in lymph node aspirate. A significant association was found between abnormal NFL and presence of trypanosomes in CSF, abnormal limb movements, difficulties in gait and coordination, and low Karnofsky index. By multivariate analysis, it was shown that increasing CSF cell number, increasing CSF protein concentration, and the absence of lymph nodes or the absence of trypanosomes in the lymph node aspirate were the best predictors for astrogliosis and neurodegeneration among the variables tested. These results demonstrate the importance of CSF cell count and protein determination in assessment of the severity of central nervous system involvement and reinforces the importance of laboratory diagnosis to assess the stage of the disease. The clinical symptoms studied were less useful in predicting astrogliosis or neurodegeneration.