The antibody SMI 31, which is directed against a phosphorylated epitope, associated with neurofilaments and recognizes Lewy bodies in brains of patients with Parkinson's disease (Bancher C, Lassmann H, Budka H, Jellinger K, Grundgke-Iqbal I, Iqbal K, Wiche G, Seitelberger F, Wisniewski H: J Neuropathol Exp Neurol 1:81, 1989), decorated in immunofluorescence microscopy Mallory bodies (MBs) present in livers of mice chronically treated with griseofulvin and 3,5-diethoxycarbonyl-1,4-dihydrocollidine. In immunoblots it recognized very acidic MB components in a molecular weight range between 55 and 69.5 kilodaltons in addition to poorly soluble high molecular weight material. Moreover, an antibody to tau protein showed similar reactivities in immunofluorescence microscopy and immunoblotting experiments. Both antibodies also stained MBs in human liver with alcoholic hepatitis. These observations support and extend earlier findings which indicate that several intermediate filament-related cellular inclusion bodies, including MBs, share a variety of morphologic, structural and antigenic features. They also suggest the involvement of tau or tau-like proteins in MB formation.