Postoperative ectopic bone formation affects about 40% of people undergoing elective hip replacement surgery. Despite clear evidence that a short course of perioperative nonsteroidal anti-inflammatory drugs (NSAIDs) can substantially reduce the occurrence of ectopic bone, the use of NSAID-based prophylactic therapy is uncommon in Australia or New Zealand. In part, this reflects surgeons' uncertainty about the importance of ectopic bone as a cause of impaired long-term outcome, and in part, concerns about possible increased risk for gastrointestinal complications and excess wound bleeding in patients undergoing orthopedic surgery. To address this uncertainty, a multicenter randomized controlled clinical trial is being conducted amongst 1000 patients undergoing elective total hip replacement (or revision) surgery. Patients are randomly allocated to 14 days of treatment with either 1200 mg ibuprofen (a commonly used NSAID) or matching placebo commencing within 24 h of surgery. Treatment outcomes will be assessed 6–12 months later. The primary outcome will be self-reported pain and physical function. Secondary outcomes include quality of life and physical performance measures. Patient recruitment has commenced in more than 20 orthopedic centers throughout Australia and New Zealand and will be complete by the end of October 2003. The prevention of chronic ectopic bone-related pain and disability after hip replacement surgery with anti-inflammatory drugs study (HIPAID) has been designed to provide precise and reliable information about the overall balance of risks and benefits associated with a short 14-day perioperative course of ibuprofen among individuals undergoing elective total hip replacement surgery.