Thirty-three patients with bone tumor(malignant in 10 cases and benign in 23 cases)selected from Department of Bone Tumor,the Second Affiliated Hospital of Mongolian Medical College from October 1999 to August 2006 underwent special prostheric replacement at neoplastic segment.The prosthesis was made of stainless steel, alloy of cobalt-chrome-molybdenum,or titanium alloy,which are provided by Beijing Lidakang Technology Company Limited.All patients provided the conftrmed consent.In the follow-up of 6-70 menths,one patient with giant cell tumor of haunch bone,two patients with malignant synovioma,and one patient with malignant fibrous histiocytoma died due to pulITlonary metastasis.In all those patients who survived,none have local recidivation,transferring,or fracture.Among them,one patient had postoperative infection and rigor at knee joint.Three patients had ache at middle part of thigh(junction between prosthesis and femoral bone)after knee joint replacement.According to the Ennekhag scores after reconstruction of surgical oncology,fineness rate of upper limbs was 80%,and that of lower limbs was 86.4%.Odynolysis rate of shoulder ioint was 90%.Active movement was increased and activity of femoral articulation Was generally normal.Extension and flexion of knee joint ranged from 0 to 100 degree.Rejection occurred in stainless steel prosthesis of knee joint in one patient.Junction between prosthesis and femoral bone Was looge in two cases.All other prostheses had great biocompatibillty to tissues.