The results of the radiosynoviorthesis with yttrium-90 silicate in 36 joints, are reported. In comparison to the radiogold therapy in 64 joint, yttrium-90 was a little more effective. Additionally, the body distribution of radioactive yttrium after radiosynoviorthesis of knee joints, was measured in 6 patients. It could be shown that the uptake of the regional lymphnodes was between 4 and 5% of the yttrium administered. The radiation dose of the regional lymphnodes certainly exceeds 1000 rad. The results point to the importance of a careful selection of patients for radiosynoviorthesis.