Radiosynoviorthesis is a safe and easy method for synovectomy in haemophilic arthropathy. Various agents have been used in radiosynoviorthesis, especially newly developed agent Holmium-166-chitosan complex has good clinical outcome. This study analysed clinical results and radiologic evaluation of radioisotope synoviorthesis using Holmium-166-chitosan complex in haemophilic arthropathy. From March 2001 to December 2003, 58 radiosynoviorthesis were performed in 53 haemophiliacs. The average age at procedure was 13.8 years. The Arnold and Hilgartner stage of the patients was from I to IV. Holmium-166-chitosan complex was injected in 31 ankle joints, 19 elbow joints and 8 knee joints. Average follow-up was 33 months since primary procedure. The range of motion of each joint, frequency of intra-articular bleeding and factor dose used were analysed for clinical assessment. There was no significant improvement of range of motion in affected joints. After procedure, the average frequency of bleeding of the elbow joint has decreased from 3.76 to 0.47 times per month, the knee joint from 5.87 to 1.12 times per month, and the ankle joint from 3.62 to 0.73 times per month respectively (P < 0.05). After treatment, the average coagulation factor dose injected was significantly decreased to 779.3 units per month from 2814.8 units per month before treatment (P < 0.001). Radioisotope synoviorthesis with Holmium-166-chitosan complex in haemophilic arthropathy is a very safe and simple procedure with the expectation of a satisfactory outcome without serious complication. It has excellent bleeding control effect on target joint and the need for substitution of coagulation factor concentrate can be reduced.