Synoviorthesis with radioisotopes is indicated when joint inflammation is not totally controlled by drug prescription. Synoviorthesis should prevent osteoarticular destruction, especially in those cases where the patient does not feel any pain while taking analgesic and anti-inflammatory drugs. Several publications have shown the value of 90Y for treatment of the knee in rheumatoid arthritis. A dose of 4 mCi seems to be sufficient. For digital joints 169Er, a much weaker isotope, is used. Excellent and good results are obtained in 54.6% of cases. A recent double-blind study demonstrated a highly significant difference with saline (+ prednisolone acetate). Other joints, such as the wrist, elbow, shoulder, ankle or hip, can be treated with 198Au or, better, with 186Rh, which is an almost pure beta-emitter. Excellent and good results are seen in 50--60% of cases, depending on the joint. Treatment is well tolerated but patients younger than 40 years should not receive isotopes and the total dose administered should be less than 15 mCi.