Recent data support an important role played by nuclear factor kappa B (NF-kappaB) in peripheral neuropathies. We investigated expression and activation of NF-kappaB in experimental autoimmune neuritis (EAN) in rat sciatic nerves removed after 7, 14 and 21 days after immunization. Immunoreactivity for the activated form of NF-kappaB was found in the nuclei of T cells and macrophages at days 14 and 21, and also in the nuclei of few Schwann cells and of vascular endothelial cells at all time points, especially during the peak stage. Western blot showed a single band corresponding to 65 kDa in all EAN animals. NF-kappaB DNA-binding activity was revealed by electrophoretic mobility shift assay. Our results support NF-kappaB activation in EAN during the induction stage as well as in the disease remission.