The management of the large segmental defect of the long bone after the failure of multiple surgical attempts is a difficult problem especially in cases caused by the infection. Authors performed allograft transplantation in 7 cases of the large segmental defect of the long bone from April 1987 to April 1991. The results were as follows; 1. The major cause of the large segmental defect of the long bone was the infected non-union. 2. The average bone defect remaining after debridement was 8.1cm (range from 4cm to 13cm) and the average length discrepancy of the limb was 2.6cm (range from 0cm to 4cm). 3. The average length of the allograft was 10.5cm (range from 4.5cm to 16cm). 4. In the cases of the infected non-union, the operation was performed average 10 months after the subsidence of the sign of the infection. 5. The mean duration of the follow-up was 40.4 months (range from 22 months to 70 months). 6. The bone union was achieved in four cases and the mean time was 12.8 months. Two cases have been followed up for 24 and 31 months each and they showed complete bone union in one side of the host-graft junction, but not complete union in another side. In one case, developed the osteolysis of the grafted bone due to the infection. After operation, the average length of limb length discrepancy was 1.3cm (range from 0cm to 2cm).