Cleavage at cysteine and chymotrypsin digestion were applied to two human neurofilament (NF) subunits, low- and high-molecular-weight NF (NF-L and NF-H), to locate the regions reacting with Bodian's silver stain and with several monoclonal antibodies, including NF-specific antibodies and one that recognizes all intermediate filaments (anti-IFA). Our findings indicate that whereas anti-IFA recognizes the highly conserved rod domain, all the NF-specific antibodies, as well as Bodian's silver, react with the carboxy-terminal tailpiece of NF subunits. The silver binding sites in NF-L are located in a carboxy-terminal 12-Kd chymotrypsin fragment, a highly charged, unique domain of NF.