Between 1994 and 1999 we performed 66 Yttrium-90 (90Y) synoviortheses on 44 persons with haemophilia (45 knees, 12 elbows, nine ankles). At the time of injection 23 patients were HIV+ and two had inhibitors. The average age was 21.1 years (range: 9-39). Five mCi of 90Y were injected into the knees, and 3 mCi into the elbows and ankles. The average follow-up was 3.5 years (range: 1-6). Of the 45 knees, there were eight excellent, 10 good, 15 fair and 12 poor results. Of the 12 elbows there were three excellent results, five good, three fair and two poor. Of the nine ankles there were no excellent results, four good, three fair and two poor. The elbows had better results than the knees and ankles. The best results were obtained in the youngest patients, and in those with a moderate degree of synovitis, regardless of their HIV status and the presence of inhibitor. 90Y synoviorthesis should be performed in very young patients, when the amount of synovium is still moderate. Once the degree of synovitis has become severe, the expected results of radioactive synoviorthesis are worse.