This prospective study evaluated heterotopic ossification prophylaxis with indomethacin for 14 days in 201 consecutive patients undergoing total hip arthroplasty. Ranitidine was administered concurrently to alleviate gastrointestinal side effects. None of the patients with mild gastrointestinal side effects (12%) had to suspend the prophylaxis, and no major postoperative bleeding or gastrointestinal ulcers were observed. After 12 months of follow-up, 67% of patients had no evidence of heterotopic ossification, 32% percent had grades I and 1% had grade III without clinical significance, and 0% had grade IV ossification according to Brooker's classification. These results indicate that short-term indomethacin prophylaxis is an effective, inexpensive, and easily administrated alternative to single-dose radiotherapy for nearly all patients undergoing THA.