This study was performed to determine the utility of sympathetic skin response (SSR) in evaluating the sympathetic function and to follow up the effects of sympathetic blockade in reflex sympathetic dystrophy (RSD). Thirty patients having RSD with upper extremity involvement were randomly divided into two groups. Besides medical therapy and exercise, physical therapy agents were applied to both the groups. In addition to this treatment protocol, stellar ganglion blockade was done by diadynamic current in Group II. The normal sides of the patients were used for the control group. SSRs were measured in all the patients before and after the therapy. The amplitude was found to be increased and the latency was found to be decreased in the affected side in both the groups before the therapy. After the therapy, the amplitude was decreased and latency was increased in both the groups. But, the differences in amplitude (P=0.001) and latency (P=0.002) before and after the therapy were significantly higher in Group II. (Before the treatment, SSRs were significantly different between the normal and the affected sides in both the groups. The observed change in SSRs after the treatment was higher in Group II.) It was concluded that, SSR can be a useful and noninvasive method in diagnosing the sympathetic dysfunction in RSD and can be used for evaluating the response to sympathetic blockade and other treatment modalities.