In the reported series of 35 cases bone reconstruction of large diaphyseal defects was performed in two stages. The first stage was the insertion into the defect of a cement spacer which was responsible for the formation of a pseudosynovial membrane. The second stage was the reconstruction of the defect by a huge fresh autologous cancellous bone graft. The membrane induced by the spacer prevents the resorption of the graft and favors its vascularity and its corticalisation. In weight bearing diaphyseal segments the normal walking was possible at 8.5 months on average. The length of the reconstructed defects was 4 to 25 cm.