147 patients due to have a cemented total hip arthroplasty were randomized to 4 groups. They received either tenoxicam 20 mg or 40 mg, or placebo, for 5 days or morphine on the day of operation and placebo for 4 days. During the first 5 days 14 patients were excluded. The patients were followed for 1 year, during which another 10 patients were excluded. At follow-up, significantly fewer patients had heterotopic ossifications in the tenoxicam groups than in the placebo and morphine groups. There was no significant difference between the 2 tenoxicam-treated groups, and we therefore conclude that tenoxicam 20 mg for 5 days postoperatively can reduce heterotopic ossification after cemented total hip arthroplasty.