We studied the effects of short-term therapy with methylprednisolone and indomethacin on healing of intramedullary pinned osteotomies of the femur in rats. When the osteotomy was complete and healing occurred under unstable conditions with callus formation, indomethacin inhibited healing when estimated by mechanical tests of bending moment, energy expenditure before refracture, and bending rigidity 6 weeks after surgery. No inhibitory effects were seen following corticosteroid treatment. When the osteotomy was incomplete and healing occurred under stable conditions, similar tendencies were observed. Thus, short-term medication with indomethacin inhibits fracture healing. This was not the case with short-term methylprednisolone.