Using the indirect immunofluorescence technique, a study was made of the distribution of the major cytoskeletal proteins in cultures of cells derived from chicken embryo and newborn rat dorsal root ganglia. An antibody raised against the 200 000 molecular weight neurofilament "triplet" polypeptide isolated from rat sciatic nerve strongly stained some, but not all neurones in these cultures. In contrast filamin and vimentin antibodies stained Schwann cells and fibroblasts but not neurones. Antibody to fibronectin only stained material associated with fibroblasts. Thus these four antibodies can be used to distinguish between neurones, Schwann cells and fibroblasts, as well as to detect a heterogeneity in the neuronal population. In addition these antibodies, plus antibodies to actin, myosin, alpha-actinin, tropomyosin, fimbrin and tubulin allow a more detailed description of the cytoskeleton of cultured neurones at the light microscopic level.