The functional outcome of total hip arthroplasty for arthrodesed hips was evaluated. During the years 1979 to 1988, 55 arthrodesed hips were converted to total hip arthroplasties. Thirty-seven women and nine men were followed for a minimum of 5 years. Thirteen of the patients were very much satisfied with the operation, 19 were much satisfied, 7 were satisfied, 3 were less satisfied, and 4 were unsatisfied. The Harris hip score was improved from 51-83 at the time of operation to 53-93 at the follow-up examination. Before conversion, none of the patients used crutches. At the follow-up examination, 10 patients used two crutches, 24 used one crutch, and 12 did not need support. Muscle strength of the abductors ranged from 1 to 4. In 26 patients with major low back pain before conversion, the pain score improved from 3-10 at the time of operation to 0-8 at the follow-up examination. This study shows that with conversion of an arthrodesed hip to arthroplasty, most patients need support for walking; however, they are generally grateful for their new mobility, maneuverability, and improved ability to sit comfortably.