Reflex sympathetir. dystrophy syndrome (RSDS), known also as Sudecks atrophy, is an uncomrnon disoder recognized by its distinctive symptom complex consisting of pain and tenderness, vasomotor instability, swelling, and dystrophic skin changes and radiologic changes. The present study has been carried out to prospectively establish scintigraphic diagnostic criteria for RSDS using three-phase radionuclide bone scintigraphy (TPBS). In addition, the csefulness in the evaluation of treatment of RSDS was assessed. Patients included were 6 men and 7 women with the age ranging from 25 to 63 years (average 47 years). Diagnosis was based on typical clinical symptoms and signs as described above. Associated r.linical conditions in these patients were cerebral infarction (4 patients), lung cancer (2 patients), trauma (1 patient), lymphoma (1 patient), and unknown cause (5 patients). All patients showed diffuse radionuclide accumulation in juxtaarticular region on the delayed static image and 11 patients showed diffusely increased activities also on scintiangiogram and blood-pool image. Fillow-up TPBS after corticosteroid therapy in 4 patients revealed near normal return of abnormal radionuclide accumulations in the affected hand. TPBS is an useful test for the diagnosrs of as well as the evaluation of the therapeutic effects of RSDS.