Terminal motor innervation and the histochemical profile of muscle fibers were investigated, before and after sciatic nerve crushing, in 1- to 150-day-old myopathic hamsters. The observed morphologic abnormalities in terminal motor innervation were of varying degree prior to the nerve injury. These abnormalities were found in close proximity to lesions of the myofibers, and became more pronounced with age and the progression of the disease process. Collateral ramification of healthy axons occurred in hamsters of 120 days of age with reinnervation of damaged muscle fibers. When submitted to sciatic nerve crushing, myopathic hamsters showed an ability to regenerate and reinnervate the subneural apparatuses. The regenerative process in these animals was essentially the same as in normal, sciatic nerve-crushed hamsters. Thus, it was concluded that the morphologic changes in terminal motor innervation were secondary to muscle cell degeneration.