Four patients were treated with limb lengthening to correct a leg-length discrepancy that developed after a hip transposition after pelvic resection for sacroma of the pelvis. Three patients had Ewing's sacroma and one patient had osteosarcoma. All patients received chemotherapy; radiotherapy also was administered to the three patients with Ewing's sacroma. Femur lengthening was started at an average of 5.7 years (range, 4.4-6.8 years) after tumor surgery. At the start of elongation, the average age of the patients was 17.3 years (range, 10.3-20.8 years). The average leg-length discrepancy was 10.3 cm (range, 6-12 cm). The average of achieved lengthening was 6.4 cm (range 6-7.5 cm). The average healing index was 32 days (range, 27-40 days) per 1-cm elongation. According to the classification of Paley, two problems and two minor complications were treated by additional interventions. At the final followup, the average functional score was 22 (73%) according to the system of the Musculoskeletal Tumor Society. Leg-length discrepancy after hip transposition can be corrected with distraction osteogenesis. All patients who wore a stiff ankle-foot orthosis before lengthening wore an ordinary shoe lift after lengthening. The problems of the lengthening procedure are similar to the general complication rate of bone lengthening. Because the 5-year survival after resection of a pelvic sarcoma is only 20% to 30%, leg lengthening after hip transposition should be offered only to long-term survivors with at least 5 years event-free survival.