Previous immunocytochemical studies have shown immunological differences between neurofilaments in axons and those in dendrites and perikarya of many mature neuron types: it is now known that non-phosphorylated epitopes are normally seen in cell bodies and dendrites of mature neurons, whereas phosphorylated epitopes are observed in axons. Further studies on a variety of cell types have shown that phosphorylated epitopes are induced in the cell-body associated neurofilaments following axotomy, and we show here that comparable changes are observed in axotomized rat superior cervical ganglion neurons (SCG). We have also observed that preganglionic section induces similar changes in the levels of neurofilament phosphorylation, so that phosphorylated epitopes become visible in the cell bodies and dendrites of denervated neurons. The changes in this case appear more slowly and are accompanied by the appearance of punctate nuclear staining detectable with phosphorylation sensitive neurofilament antibodies. The acquisition of these staining patterns by both the axotomized and denervated SCG cells proved to be reversible, so that after 10-12 days no neurons in either experimental group exhibited perikaryal phosphorylated epitopes. These results indicate that changes in the level of neurofilament phosphorylation are not only associated with neuronal damage, but can also be induced by deafferentation.