Objectives: Radionuclide synovectomy is a reliable therapy in patients with chronic synovitis. However, radiation doses delivered to non-target organ systems due to leakage of radioactive material from the articular cavity are an important disadvantage of this procedure. In this study we compared extraarticular leakage values of the 3 commonly used radiopharmaceuticals; Y-90-citrate, Y-90-silicate and Re-186-sulfide colloid. Materials and Methods: Thirty-five patients with persistent synovitis were enrolled in the study. Twenty-two hemophilic, 8 rheumatoid arthritis and 5 patients with pigmented villonodular synovitis were studied. Y-90 labeled silicate and citrate were used for knee joints and 186Re-sulfide for intermediate sized joints. Radiocolloid leakage values were evaluated using a gamma camera with 20% window centered over the bremsstrahlung photopeak of Y-90 and a respective window over the 137 keV photopeak of Re-186. Regions of interest were drawn over the injection site, the regional lymph nodes and the background areas. Leakage of radiocolloid was calculated by dividing the counts/pixel in the regional lymph node area to the counts/pixel in the injection site. Results: No visible leakage was observed. The median leakage values calculated for Y-90-citrate, Y-90-silicate and Re-186-sulfide were found as 1.9%, 2.4% and 2.7%, respectively. The difference between the variability of leakage values was not statistically significant (p > 0.05). Conclusion: There was no significant difference in terms of extraarticular leakage between Y-90-citrate, Y-90-silicate and Re-186-sulfide radiocolloids.