A double-blind prospective parallel group study comparing slow-release flurbiprofen with placebo in the control of ectopic bone formation was carried out in 68 patients undergoing total hip arthroplasty. Eight weeks after surgery there was evidence, significant at the 1% level, that the incidence and extent of periarticular calcification was lower in the flurbiprofen group. At an early phase, serum calcium level decreased and after 8 weeks serum alkaline phosphatase level increased more in the placebo group than in the flurbiprofen group, indicating an effect of flurbiprofen on bone mineral metabolism. Six patients were withdrawn in each treatment group, four due to side effects in the flurbiprofen group and three due to side effects in the placebo group. Overall, five patients in each group reported side effects, the nature and severity of the side effects being very similar in each group. We conclude that flurbiprofen is an efficient and safe drug in limiting ectopic bone formation following total hip arthroplasty. Heterotopic bone formation is a frequent complication after total hip replacement [1,2,[4][5][6][8][9][10][11][12][13][14][15][16]. Heterotopic bone reduces the extent of hip motion, reduction being more evident in cases with extensive ectopic bone formation around the hip joint [3,10,11]. Various treatment regimens have been proposed for discouraging heterotopic bone formation. Anti-inflammatory agents such as indomethacin and ibuprofen have turned out effective [11,12,14]. Local irradiation also prevents ectopic bone formation [4], but diphosphonates seem not be effective in this respect [15]. The aim of the present study was to assess the efficacy of flurbiprofen, a new anti-inflammatory agent, in limiting heterotopic bone formation, and to note the frequency and severity of any side effects of the treatment.