In 23 patients with reflex sympathetic dystrophy (RSD) of the hand, scintigraphy with indium-111 labeled human non-specific polyclonal immunoglobulin G (In-111-IgG) was performed to investigate whether inflammatory characteristics are present in RSD. Both blood flow and accumulation over 48 h were assessed. Nineteen patients had increased flow to the affected hand, and 3 had decreased flow. One patient had bilateral RSD. Exercise provoked aggravation of complaints and signs in all patients. The affected/non-affected hand ratio (target-to-background, T/B) immediately before and after exercise did not change significantly. The T/B ratios 48 h after In-111-IgG injection were significantly higher in patients with RSD less than 5 months than in patients with RSD existing 5 months or longer. The T/B ratios 24 and 48 h after In-111-IgG injection were not correlated with the flow T/B ratios. In fact, 2 of the 3 patients with a decreased flow showed excess accumulation on the late images. Significantly more patients with early RSD, existing less than 5 months, had a positive In-111-IgG scintigraphy (14 of 17) than the patients with late RSD (1 of 6). Increased vascular permeability for macromolecules, an important characteristic of inflammation, appears to play a role in the development of RSD. This phenomenon is not flow-dependent.