This study was designed to elucidate the existence of PSD95 in the rat sciatic nerve. Immunohistochemical stains of cryosection and teased fiber of sciatic nerves were performed with goat polyclonal antibody against PSD95. Western blot analysis was also accomplished with the same antibody. We got an interesting result that the rat sciatic nerve obviously showed PSD95 immunoreactivity especially in the nodal and paranodal regions, and we also identified a distinct band of PSD95 by western blot. These results suggest PSD95 exists in the sciatic nerve as well as it does in the central nervous system. We suppose PSD95 may have some important roles in ion channel clustering, junctional plasticity and signal transduction in the peripheral nerves as well.