After demonstrating initial safety of Ibuprofen administered to hemophiliacs, a 16-wk double-blind individual crossover trial was designed to test the safety and, to a more limited extent, the efficacy of 1600 mg of Ibuprofen or placebo given daily to 20 hemophiliacs with hemophiliac arthropathy. The trial was completed with no evidence of increased frequency or severity of hemophiliac bleeding episodes or clinical or laboratory evidence of bleeding secondary to Ibuprofen. There were five treatment failures, none associated with hemorrhage or lack of compliance. A benefit was obtained in reduction of early morning stiffness and pain. Ibuprofen should be considered as a safe and potentially beneficial antiinflammatory agent in the treatment of carefully monitored hemophiliacs eligible for such therapy.