Proteins of lumbosacral spinal roots and sciatic nerves of adult dystrophic mice (Bar Harbor 129REJ dydy) were analyzed by SDS gel electrophoresis to determine if identifiable proteins were affected. All peripheral nerve myelin proteins (P0 glycoprotein, P1 and Pr basic proteins, X protein and a high-molecular-weight protein) were decreased in the roots but not in the sciatic nerves. Central nervous system myelin proteins were not increased in either roots or sciatic nerves. Although dystrophic spinal roots and sciatic nerves contained less collagen, Type I, III and V collagens were present.