Autotomy and the concentrations of beta-endorphin and Met-enkephalin in brain areas and the spinal cord were measured in Sprague Dawley, Wistar and Wistar Lewis rats thirty-five days after the section of one sciatic nerve. As expected, autotomy developed in Sprague Dawley and Wistar, but not in Wistar Lewis rats. In the Wistar Lewis, brain and spinal cord concentrations of Met-enkephalin increased, beta-endorphin concentrations were unchanged. In Wistar and Sprague Dawley rats the increase of Met-enkephalin was accompanied by a decrease of beta-endorphin. Administration of chlomipramine, a drug usually employed in the treatment of deafferentiation pain, normalized the concentrations of beta-endorphin in the Sprague Dawley and Wistar rats, and avoided the development of autotomy, while Met-enkephalin concentrations did never change. The data presented suggest a possible correlation between beta-endorphin and autotomy.