Aim. The use of megaprostheses for knee reconstruction after distal femur resection in young bone sarcoma patients has become popular since early ′80. The authors reviewed their experience with different distal femur megaprostheses in children. Method. Clinico-radiographic evolution in a consecutive series of 113 children, that had implanted below age 15 (range 6-14) a distal femur megaprosthesis in the period 1984-2007, was analized. A modular implant was used in 97 cases with uncemented femoral stem (three different models along the period). The implant presented fixed-hinge joint in 78 cases while rotating-hinge knee was utilized in 19 cases. In 39 cases the fixed-hinge joint had a tibial component with a polished stem to allow the residual growth of proximal tibia; in two cases a mechanically extendable prosthesis was used. A custom-made noninvasive extendable prosthesis with cemented femoral stem and smooth uncemented tibial stem was used in 15 cases since 2002. Radiological and functional results were analysed and a statistical comparison of implant outcome according different stems was obtained. Results. At a 74 months follow-up (29-294), 72 patients are alive; but 43 of them (60%) had further surgery related to primary implant. Surgical revision rate was 88% (39% for mechanical failure) in long survivors treated before 1995 and 50% (14% with mechanical failure) in more recent cases (p< 0.05). Three long survivors progressed in time to total femur megaprostheses. Five out the 15 cases treated by custom made expandable prostheses were revised before completion of skeletal growth because of implant failure. Conclusion. In limb-salvage for bone sarcoma, megaprostheses are the preferred method to reconstruct distal femur in growing children, but a durable reconstruction is not easy to be achieved. The use of new devices specially addressed to younger patients deserves a serious scientific survey by musculoskeletal oncology community