We retrospectively reviewed 54 patients (92 hips) who underwent cementless total hip arthroplasty for bony ankylosis in ankylosing spondylitis between September 1988 and 2002. The mean age of the patients was 25.5 years. The mean duration of follow-up was 8.5 years. The average preoperative Harris Hip Score of 49.5 improved to 82.6 postoperatively. Postoperatively, 10 hips had mild to moderate pain. Anterior dislocation occurred in 4 (4.3%) hips, and sciatic nerve palsy in 1 (1.1%) hip. Heterotopic ossification was seen in 12 patients; reankylosis rate was 0%. Thirteen (14%) arthroplasties were revised because of aseptic loosening. Kaplan-Meier survivorship analysis with revision as end point revealed 98.8% survival at 5 years and 85.8% survival at 8.5 years follow-up.