A total hip arthroplasty was undertaken in a 49-year-old man who had previously spontaneously ankylosed both hips. In addition, the patient possessed hyperostosis of the spine and calf, not characteristic of any previously described spondylitic or hyperostotic syndrome. Nine months postoperatively the patient reankylosed the total hip arthroplasty. This case provides further evidence that total hip arthroplasty must be undertaken with caution in patients with hyperostotic tendencies.