Adult rabbits were divided into three equal weight-matched groups. Drill holes 2.3 mm in width were drilled through the midshaft of the right femur across both cortices. A sham operation was performed on the left femur and served as a control. Group I was given indomethacin, 5 mg/kg twice daily. Group II was given ibuprofen, 7.5 mg/kg twice daily. Group III was given a placebo solution. Each group was treated for five or eight weeks. The serum levels of indomethacin and ibuprofen were recorded during treatment. After the rabbits were killed the legs were dissected from soft tissue and stored in a freezer. After thawing, the bones were examined for torsional strength. Neither the indomethacin nor the ibuprofen groups regained their torsional strength during the treatment periods, as compared with the controls. Anti-inflammatory drugs probably bring about their effects by acting on the prostaglandin synthesis. Although the effects produced by the drugs are significant, it is still uncertain whether the effects are great enough to influence one's decisions regarding their use.