To raise this antibody bovine intermediate filaments were prepared from spinal cords by the method of Delacourte et al. and the cytoskeletal material was dissolved in 6M urea. Individual neurofilament subunits were purified by ion exchange chromatography on DEAE cellulose followed by preparative gel electrophoresis. To ensure greater specificity for NF-L, animals were boosted with recombinant mouse NF-L purified from bacteria.