PURPOSE: The appearance of scintigraphic and magnetic resonance imaging during the evolution of reflex sympathetic dystrophy of the foot is not well known and subject to controversies. The purpose of this preliminary study is to compare these two types of investigation during the first 6 months of evolution. METHODS: 4 non-selected patients with a diagnosis of acute reflex sympathetic dystrophy of the foot (no more than 2 months of evolution and more than 3 out of 6 clinical criteria suggesting a "warm" phase) were studied prospectively. A clinical evaluation, scintigraphy and magnetic resonance imaging (MRI) were performed at diagnosis and after 3 and 6 months. All available examinations (n = 22) were analyzed independently by independent observers. RESULTS: Clinically 3 of 4 patients developed or previously had another site of sympathetic dystrophy confirmed by total body scintigraphy. After 6 months 2 of 4 patients still have a "warm" dystrophy. Bone scanning showed localized or diffuse tracer uptake and MRI showed bone and soft tissue edema when the sympathetic dystrophy was and/or remained clinically "warm". MRI bone edema moved from one location to another in 3 of 4 patients during the follow-up. There was a good correlation between bone scan and MRI images. In "warm" dystrophy, MRI was positive 5 out of 7 times and scintigraphy in all cases. Bone edema and tracer uptake faded simultaneously although the latter was more diffuse and more persistent than the former. CONCLUSION: MRI as well as bone scintigraphy are suitable for the diagnosis of warm dystrophy of the foot. Both exams remain positive when the dystrophy is still "warm" after 6 months. The radiographic evolution after 6 months still has to be evaluated.