PURPOSE: To introduce and report the results of treatment of old patients' infected nonunion using external fixator. MATERIALS AND METHODS: Nine patients more than 60 years old were included in the study. Four cases had combined medical problems of diabetes, hypertension, and vascular disorder. We used Ilizarov fixator in eight cases and uni-lateral external fixator in one. All patients were treated with debridement, broad sequestrectomy, segmental resection, bone graft and compression of fracture site about 1~1.5 cm. We evaluated the final results by functional result and complication according to the criteria of Paley. RESULTS: Average length discrepancy was 1.7 cm before operation by initial bone loss and final follow-up shortening was average 2.6 cm. Mean duration of fixtor removal was 5.2 months. We acquired bony union lastly in 8 cases. Final functional result was 3 excellent, 2 good, 2 fair and 2 poor. Among them, 2 good, 1 fair and 1 poor cases had medical problem. CONCLUSION: In old patients, compression of nonunion site and early joint motion using external fixator seemed to be very useful in the treatment of intractable infected nonunion of lower extremity and in minimizing duration of treatment.