The aim of this prospective study was to evaluate the efficiency of radiation synovectomy with rhenium-186 or erbium-169 in rheumatoid arthritis. In the control groups articulosynovitis was treated by injection of triamcinolonhexacetonid. Follow-up time was 3 years. Patients of the study had to fulfill the following criteria: rheumatoid arthritis (ARA criteria 1988), patient age above 40 years, standardized medical treatment with methotrexate, (started at least 6 month prior to injection therapy, given for the entiry study time), prednisolon < or = 7.5 mg/d and diclofenac < or = 150 mg/ d, and no previous surgery or injection therapy on this/these joint/s. Shoulder, elbow, wrist, and ankle joints were treated in group 1 by injection of rhenium-186 combined with triamcinolonhexacetonid, in group 2 by injection of triamcinolonhexacetonid alone. Each treatment group included 50 joints. Digital joints underwent injection of erbium-169 combined with triamcinolonhexacetonid (group 3 = 131 joints) or triamcinolonhexacetonid (group 4 = 86) alone. During the follow up period, the joints were assessed for pain, synovial swelling, joint motion, and stage of radiological destruction (Larsen-Dale-Eek). After 3 years follow-up, 228 joints met the above named criteria: group 1 = 41 joints, group 2 = 21 joints, group 3 = 131 joints, group 4 = 53 joints. Significantly better clinical results were achieved with the combined injection of rhenium-186 or erbium-169 and triamcinolonhexacetonid. Results for PIP joints were worse than for other joints, which is explained by better immobilization of the latter ones after injection. The progression in radiological joint destruction according to the stages of Larsen-Dale-Eek during the follow-up time of 3 years (= stage at 3 years minus stage prior to treatment) corresponded to the clinical results and was significantly slower in groups 1 and 3: group 1 = 0.62; group 2 = 1.7; group 3 = 0.75; group 4 = 1.43 Therefore, we recommend radiosynovectomy with erbium-169 or rhenium-168 in combination with triamcinolonhexacetonid and consequent immobilization after injection.