Sixty-four patients were evaluated prospectively for a reflex sympathetic dystrophy syndrome (RSDS), using quantitative clinical measurements, high-resolution roentgenography and scintigraphy. Five separate groups were identified by their clinical features, allowing us to distinguish patients with definite or incomplete forms of the RSDS as well as 16 patients with other disorders. Scintigraphy was found to be a useful diagnostic study that may also provide a method of predicting therapeutic response. Systemic corticosteroid therapy proved to be a highly effective mode of treatment for up to 90 percent of the patients with the RSDS.