Radiosynovectomy has been performed successfully for more than 10years in our hospital. This study investigated the long-term outcome in the context of time to progression (TTP) analysis and the factors influencing TTP following radiosynovectomy with Re-186 in patients with haemophilic synovitis. Radiosynovectomy performed in 165 joints (81 elbows, 74 ankles, 8 shoulder and 2 hip joints) of 106 patients (median age was 18.0 +/- 7.5years; 91 haemophilia A, 13 haemophilia B and 2 von Willebrand's disease between June 2001 and July 2011. The mean follow-up was 48months (range: 9120months). This study revealed that patients' mean TTP after primary radiosynovectomy was satisfactory for both the ankle and elbow joints. There was no TTP differences between the ankle and elbow joint groups (67 vs. 72months respectively; P=0.22). We did not find a relationship between the TTP and the following variables: age, type and severity of haemophilia, the presence or absence of inhibitor, the radiological score, range of motion (ROM) status of joints and the pretreatment bleeding frequency. In this study, 1820% of the treated joints had improved ROM and 8279% of the treated joints had unchanged ROM after treatment both the ankle and elbow joints respectively. In this report including TTP analysis in the largest series with long-term follow-up, we demonstrated long-term effectiveness of Re-186 radiosynovectomy in haemophilic synovitis. In our experience, the main predictor of outcome following radiosynovectomy is the number of joint bleeding within 6months after therapy.