Tumor necrosis factor (TNF) is thought to be one of the mediators responsible for the damage of oligodendrocytes (OLGs) in multiple sclerosis (MS). We report here the involvement of the interleukin 1beta-converting enzyme (ICE)/Caenorhabditis elegans gene ced-3 (CED-3) family in TNF-mediated cell death of OLGs. The addition of TNF-alpha to primary cultures of OLGs that express ice and cpp32 significantly decreased the number of live OLGs in 72 h. DNA fragmentation was detected in TNF-treated OLGs at 36 h with the terminal deoxynucleotidyl transferase dUTP nick end-labeling assay. Benzyloxycarbonyl-Asp-CH2OC(O)-2,6-dichlorobenzene, an inhibitor of the ICE/CED-3 family that shows p35-like inhibitory specificity, protected against the TNF-induced cell death of OLGs. Furthermore, acetyl-YVAD-CHO (a specific inhibitor of ICE-like proteases) as well as acetyl-DEVD-CHO (a specific inhibitor of CPP32-like proteases) enhanced the survival of OLGs treated with TNF-alpha, indicating that ICE- and the CPP32-mediated cell death pathways are activated in TNF-induced OLG cell death. Our results suggest that the inhibition of ICE/CED-3 proteases may be a novel approach to treat neurodegenerative diseases such as MS.