Subacute sclerosing panencephalitis (SSPE) is a neurodegenerative disorder due to persistent measles virus infection, with high level of measles-specific antibodies in cerebrospinal fluid (CSF). To analyze whether such response arises from a TH2-biased response, the authors determined TH1 (interferon [IFN]-gamma) and TH2 (interleukin [IL]-4 and IL-10) cytokines in CSF, taken at diagnosis, of eight SSPE patients (median age, 57.5 month, range 42 to 76 months). All patients presented IL-10 (median 29.3 pg/ml, range 4.3 to 162 pg/ml), but not IL-4 (<10 pg/ml); only one case showed IFN-gamma (162 pg/ml). These results are consistent with a TH2 bias or with a local, anti-inflammatory or neuroprotective mechanism involving IL-10.