PURPOSE: To evaluate the effectiveness of Ilizarov external fixator for the treatment of unstable closed or open comminuted femoral and tibial fractures, especially those with severe soft tissue injury by clinical and radiological analysis. MATERIALS AND METHODS: Fifty six consecutive femoral or tibial fractures were treated using Ilizarov external fixator between May 1991 and August 1998 and followed up for minimum 12 months upto 36 months with the average of 16 months. All of them consisted of comminuted or segmental fractures. And thirty five cases of them were open fractures. There were nine Type I, seventeen Type II, five Type IIIA, and four Type IIIB fractures. Primary closure was performed for Type I and II fractures. Split-thickness skin graft (5 cases) and free vascularized flap (3 cases) were used for severe soft tissue defects. RESULTS: All fractures healed within the average of 7.7 months (from minimum 3 months to maximum 24 months). Bone grafts were performed in 39 cases. Bony union was obtained in all the cases with Ilizarov method. The most common complication, the adjacent joint contracture was developed in 21 cases (37.5%). Pin site infection in 12 cases (21.4%), delayed union in 3 cases (5.4%), angulation deformity in 2 cases (3.6%) were developed. CONCLUSION: The Ilizarov external fixation technique is one of the effective methods in the management of unstable closed or open comminuted femoral or tibial fractures.