Both neurons and oligodendroglia are preferentially infected in subacute sclerosing panencephalitis (SSPE). Massive argyrophilic and tau-positive glial fibrillary tangles (GFT) were found in oligodendroglia in two autopsy cases of SSPE with neurofibrillary tangles (NFT). GFT shared common phosphorylated tau-epitopes with NFT, but were negative for ubiquitin. Electron microscopically, GFT consisted of compact bundles of irregularly woven tubules. Thus, GFT in SSPE differed from NFT showing regular constriction of tubules and from GFT in some other cytoskeletal disorders in which GFT reportedly consisted of straight tubules.