Neuofilaments (NF) are members of the intermediate filament protein family. These neuron-specific filaments are the major constituents of the axonal cytoskeleton. NFs are composed of three major proteins: NF-H is the heavy molecular weight protein (200 kDa), NF-M the medium (160 kDa) and NF-L the light protein (68 kDa). The NF-L and NF-M mRNAs are detected early in the embryonal brain, with a progressive increase in their levels during development, while the NF-H mRNA is barely detectable at embryonal stages but accumulates later in the postnatal brain. This antibody labels neurons of the central and peripheral nervous system, and is a useful for the identification of tumors with neuronal differentiation.