Objective: To evaluate the functional outcome and complications of allograft replacement in management of bone tumors. Methods: Between March 1992 and September 2002, 164 patients underwent bone tumor resection and massive allograft reconstruction of bone defects. The length of the resected part ranged from 5-35 cm. The resections were dassified as marginal or wide resections of the tumor on the basis of the Musculoskeletal Tumor Society staging system. Fresh-frozen allografts were employed as osteoarticular grafts (n = 95), hemi-condylar (n = 15), massive (n = 23), allograft-prosthesis composite (n=12), intercalary grafts (n=15) or hemi-pelvic grafts (n=4). Most of the lesions were osteosarcoma and giant cell tumor of bone and located in proximal and distal femur, proximal tibia and humerus. Results: At a median follow-up of 47 months (range, 12 to 168 months) after the operation, 154 of the patients in the study were free of disease and 10 died of disease. Twenty-one (12.8%) patients had local recurrence and 38 (23.2%) nonunion. Late complications included 11 (6.7%)fractures of the allograft and 18 (11.0%) infections of the graft. Instability of the joint in the form of subluxation was noted in 13 (7.9%) patients. Ten extremities were amputated due to local recurrence or severe infection. Conclusion: Allografts can be used for reconstruction of bony defects after tumor resection. Allograft has nearly similar shape, strength, osteo-inductivity and osteo-conductivity with host bone. Allograft implantation is a high complication reconstruction method, and the risk of recurrence increases when less surgical margin achieves.