Recently limb sparing surgery is accepted as an alternative method in the management of muskuloskeletal tumors of the extremity without undue compromise to the patient s life. But the limb sparing procedure results in large osseous and soft tissue defects. To fill these defect, several options have been used such as tumor prosthesis, temporary spacer with cementation, allograft, and autograft(fresh, autoclaved, low heat treated, and extracorporeal irradiated). To identify the indica- tions ot' individual option, we studied 66 cases of musuloskeletal tumors of extremity which were treated with wide or marginal resection and reconstructive surgery from June, 1990 to June, 1997, in which 48 cases were osteosarcomas, 3 chondrosarcomas, 2 synovial sarcomas. I liposarcoma, 1 giant cell tumor, I malignant lymphoma, and 10 metastatic bone tumors. The location of the lesion were distal femur in 24, proximal tibia in 24, proximal femur in 9, proximal humerus in 6, tibial midshaft in 1. distal radius in 1, and calcaneus in 1. In Enneking stages about primary bone tumors 6 cases were IIA, 42 IIB, and 8 III. We reconstructed the osseous defect with tumor prosthesis in 22 cases, temporary spacer in 9(later, 4 cases was changed to tumor prosthesis for staged operation), allograft in 25, and autograft in 14(low heat treated in 2, irradiated in 12). Total functional result by Enneking system was 71.5% . 80.8% with tumor prosthesis, 50.5% with temporary spacer, 70% with allograft, 75.3% with autograft. Infections were occurred in 18% of the patients treated with tumor prosthesis, 34% with allograft, 0% with temporary spacer or low heated autograft, and 18% with irradiated autograft. Delayed union or nonunion was occurred in l5% of the patients treated with allograft, 40% with autograft. There were 2 cases of metal failure and 2 cases of graft fracture using autograft. In conclusion, we propose that the indication of the tumor prosthesis is for the skeletally matured patient, patient with high-grade malignant tumor, older patients, and patient who have limited life expectancy. The reconstruction with allograft have several advantages for the patients with henign bone tumor and locally aggressive or low-grade malignant tumor. The temporary spacer may be used as staged operations for the skeletally immature patient and patient who have an extreme hone and soft tissue defects after limb sparing operation. The recycling autograft may be applied to the patients at any age with minimal bony involvement of tumor. The low heat treated autograft may be useful in the patients requiring intercalary reconstruction, and the irradiated autograft may he useful in the patients with periarticular involvement.