Transcutaneous electrical stimulation was tested in 24 patients with chronic pain following a peripheral nerve injury in an extremity, in 10 patients with a good effect. All of these 10 patients displayed signs of increased sympathetic activity in addition to hyperalgesia. Sympathetic block gave complete freedeom from pain. In 14 patients with the same symptomatology but without an increased or with only very slightly increased sympathetic activity, no or an insignificant effect was obtained. Sympathetic block did not relieve the pain in this group. Transcutaneous electrical stimulation should be tried as an alternative to sympathectomy in causalgia major or minor.