Seventy-four patients undergoing total hip arthroplasty considered to be at high risk for heterotopic ossification were given 75 mg of indomethacin daily for 6 weeks after operation and studied clinically and radiographically for a minimum of 6 months. Twenty-seven patients (37%) could not complete the drug course. Of the 47 (63%) patients completing treatment, only 2 (4%) had grade IIA (mild) and no patients had more severe heterotopic ossification. No major complications were attributed to the use of indomethacin. These findings support the evidence that indomethacin can effectively prevent higher grades of heterotopic ossification following total hip arthroplasty. However, approximately one-third of the patients were unable to complete the course of drug therapy, limiting the overall usefulness of indomethacin. Surgeons prescribing indomethacin must also be aware of its contraindications and adverse effects.