Bilateral vascularized fibula graft (BVFG) is actually not a satisfying method for the replacement of metadiaphyseal defects of the femur and tibia in young patients suffering from malignant bone tumors. This reconstruction was used in five patients (two female, three male, average age 15.2 years, femur n=3, tibia n=2) undergoing metadiaphyseal resection of malignant bone tumors between November 2000 and August 2003. The median length of the defect to be bridged was 16.4 cm (range 11.5-23). In the two cases of tibia reconstruction, the ipsilateral fibula was transposed into the osseous defect (fibula pro tibia). The vessels of the contralateral fibula graft were microscopically anastomosed end-to-side upon the a. and v. tibialis anterior. For the reconstruction of femoral defects, two free fibula grafts were used. All patients had multimodal treatment according to the EURO-E.W.I.N.G 99 or COSS-96 protocol. Median follow-up was at 34 months. In all cases, R0 status was achieved. None of the patients experienced local recurrence during follow-up. Radiographic signs of osseous remodeling were detected the earliest after 2 months. Full weight-bearing on the affected leg was permitted after 8-18 months. Complications occurred in four patients (bleeding 1, infection and pseudarthrosis 1, fracture 1, plate fracture 1). None of the complications led to failure of the reconstruction or to amputation. The MSTS scores was very good in two patients, good in two, and intermediate in one. Biological reconstruction of osseous defects is always desirable when possible. Good functional and durable results can be obtained using BVFG for the reconstruction of metadiaphyseal defects of the femur and tibia.