The aim of this study was to evaluate the efficiency of radiation synovectomy with rhenium-186 in rheumatoid arthritis. In this prospective, randomized trial we compared three different treatment regimens for shoulder, elbow, wrist, hip and ankle joints: group 1, injection of rhenium-186; group 2, injection of rhenium-186 in combination with triamcinolone hexacetonide; group 3, injection of triamcinolone hexacetonide alone. Each treatment group included 50 joints. Patients included in the study had to fulfil the following criteria: (1) they had to have a diagnosis of rheumatoid arthritis (ARA criteria 1988), (2) their disease-modifying drug had to be methotrexate, started at least 6 months prior to injection therapy and given for the entire study time, (3) their nonsteroidal anti-inflammatory drug had to be diclofenac given at a dose of 150 mg/day or less and (4) they were also given prednisolone at a dose of 7.5 mg/day or less. After 3 years of follow-up, 79 joints met these criteria, i. e. 71 joints were excluded from the study: 26 joints because the patients changed the disease-modifying drug (12 joints from group 1, 4 joints from group 2 and 10 joints from group 3); 45 joints because of recurrent synovitis and second-stage treatment (21 joints from group 1, 5 joints from group 2 and 19 joints from group 3). During the follow-up period, joints were assessed for pain, synovitis, joint motion and stage of radiological destruction. Best clinical results and slowest progression in radiological destruction were achieved with the combined injection of rhenium-186 and triamcinolone hexacetonide. Therefore, we recommend this treatment for articulosynovitis with the exception of severe forms, the latter because of the effective penetration range of rhenium-186.