Sympathetic skin response was utilized to study recovery of sudomotor function in 8 patients who had digit-to-digit replantation and 9 patients who had toe-to-digit transplantation. Sympathetic skin responses evoked by median nerve stimulation or magnetic stimulation of the neck were recorded from the tip of the replanted digits or transplanted toes. The contralateral normal fingers served as controls. The mean intervals between surgery and study were 33 and 37 months, respectively, for digit replantation and toe transplantation. In normal subjects, the sympathetic skin responses recorded from the fingertip were abolished by local anesthesia or cooling of the finger, while those recorded from the palm were not affected. Ischemia of the finger only transiently affected the digit sympathetic skin responses. These data indicate that the digit responses were locally generated and mediated by unmyelinated fibers. After digit replantation, the palm and digit sympathetic skin responses were not different between replanted and normal sides. After toe transplantation, palm sympathetic skin responses were normal, but digit ones had prolonged latency and reduced amplitude. The present findings suggest that recovery of sympathetic sudomotor activity can be nearly complete in digit replantation but less satisfactory in toe transplantation.