The aim of this retrospective study was to evaluate the effectiveness of circular external fixator according with Ilisarov technique for the treatment of diaphyseal pseudarthrosis. The union rate obtained in our serie was 91%. We assessed the complications related to surgery and analysed the reasons for failed technique. Between january 1986 and february 1996, 23 patients were included in this study with a mean follow-up of 65 months. The period of external fixation was 209 days on average. 21 patients had united fractures. The failures were attributed to inadequate interfragmentary contact. The main problem during treatment was pin tract infection. The late complications included axial deformities, re-fractures and joint stiffness. Circular external fixator proved to be useful for the treatment of diaphyseal pseudarthrosis, particularly those complicated by infection or post-traumatic shortening.