We have reviewed 29 cases of very unstable diaphyseal fractures of the femur in children and adolescents treated by Kuntscher nailing. Follow up was for at least 5 years, and in most cases until after the end of growth. There were no postoperative complications, and the mean overgrowth of the femur was 7.06 mm. There was growth disturbance of the proximal femur in one case, but this did not interfere with function. We believe that Kuntscher nailing is indicated in children and adolescents with unstable high velocity fractures of the femoral shaft.