Knowledge of the actions of conventional neurotrophic factors on peripheral neurons is accumulating rapidly, and growth factors that were discovered outside the nervous system have been found to have neurotrophic actions. The nature and initiation of proximal neuronal responses to nerve injury, the interactions of Schwann cells and growth cones, and the functions of macrophages in the peripheral nervous system are all areas of active investigation. Results of the surgical treatment of injuries to the brachial plexus and spinal accessory nerve are reported.