Disarticulation of a knee joint in an 8-year-old haemophilia A patient with high inhibitor of 3450 Bethesda units (BU) is described. He had an infected compound fracture of the tibia and fibula. Surgery was successfully performed after extensive plasma exchange; administration of immunosuppressive agents such as cyclophosphamide, methylprednisolone, intravenous immunoglobulin and cyclosporine were combined with a loading dose of 100 units kg(-1) of factor VIII concentrate, followed by continuous infusion of 16 units kg(-1) h(-1) of factor VIII in the form of factor VIII concentrate and cryoprecipitate for 7 days and decreased to 8 units kg(-1) h(-1) in the form of cryoprecipitate for 19 more days. During the Ist to 7th post-operative days, the lowest factor VIII inhibitor was 18 BU and the factor VIII level ranged from < 1-2.1 IU dL(-1). On the 9th and 13th post-operative day, although the inhibitor rose to 330 and 2700 BU, respectively, there was no serious bleeding. The suture was removed on the 21st post-operative day. The inhibitor spontaneously decreased to 550, 232 and 14 BU at 1, 7 and 10 months, respectively.