Peripherin, a Triton-insoluble protein, whose distribution was found to be restricted to neurons in the rodent and human peripheral nervous system, was characterized by its electrophoretic features (isoelectric point: 5.6; molecular weight: 56,000 daltons) and by its peptidic map after limited proteolysis. Comparative peptide analysis of the 70,000-dalton subunit of neurofilaments (70K NFP), vimentin and peripherin, was performed by two different methods; limited proteolysis with Staphylococcus aureus V8 protease yields a different peptidic map for each protein; treatment with N-chlorosuccinimide, which cleaves preferentially at tryptophan residues, yields only two peptides from each protein: the size of the two fragments indicates that these proteins possess a single tryptophan residue located in the central part of the molecule. A rabbit antiserum raised against mouse peripherin decorated an intracellular filamentous network in mouse neuroblastoma NIE 115 cell line. The IgG fraction of the antiserum recognizes peripherin and the smallest subunit of the neurofilament triplet (70K NFP)--but not vimentin--whereas a monoclonal anti-70K NFP recognizes only the 70K NFP. Moreover, peripherin displays the common antigenic determinant shared by all intermediate filament proteins. Hence, we propose that peripherin represents a new member of the intermediate filament protein family, and might belong to the neurofilament class.