Purpose We investigated the effect of bilateral total hip replacement (THR) for patients with ankylosed hip joints caused by late ankylosing spondylitis (AS) and to discuss its related pre-and postoperative problems. Methods Data of 12 patients with ankylosed hip joints caused by late AS who underwent THR (24 hips) were reviewed. Each patient had both hips replaced at the same time. We assessed joint pain, range of motion (ROM) and Harris hip score (HHS) to determine postoperative results. Results Mean follow-up was 4.2 years; all hip-joint function improved, and flexion deformity was corrected. Flexion ranges were 75-105°(average 84. 4°) extension 10°~20°(average 18. 7°). HHS ranged from 15.21 points preoperation to 86.25 points postoperation. No patient experienced hip pain postoperatively, and presurgery knee and lower back pain were clearly relieved postoperatively. Conclusion Bilateral THR is an effective treatment for the ankylosed hip joint caused by late ankylosing spondylitis. When considering this procedure, attention to related preand postoperative problems must be considered.