Intractable pain and sweating dysfunction can occur in patients with reflex sympathetic dystrophy (RSD). We, therefore, investigated autonomic function by measuring sympathetic skin response (SSR) in these patients. This method provides useful information regarding the pathophysiologic changes in and clinical evaluation of RSD.Twenty-six RSD patients and 22 age-matched normal subjects were involved in our investigation. Three significant stages of RSD were classified through three-phase bone scanning of the wrist, carpal and metacarpal bones. There were 11 patients in stage I RSD, nine in stage II and six in stage III. SSRs were recorded from the bilateral palms of each subject simultaneously using electrical stimulation of the median nerve in the wrist. Latency and amplitude side ratios were calculated and compared with the control group.The affected/normal (A/N) hand amplitude ratios were significantly lower in stage I RSD, and stage II RSD patients exhibited significantly higher A/N amplitude ratios compared with the control group. A/N amplitude and A/N latency ratios in stage III RSD did not change significantly. The A/N latency ratios in stage I RSD were significantly higher than those of the control group and those of stage II RSD. In one stage I patient and three stage III patients, SSRs were bilaterally unobtainable.It appears that abnormal SSRs may be associated with autonomic disturbance in RSD patients.