Osteonecrosis of the femoral head was induced experimentally in chickens after the administration of a high dose of corticosteroids. Lovastatin was used to prevent the effects of the steroid on adipogenesis in cultured cells, and adipogenesis and osteonecrosis in chickens. The in vitro study, with marrow cells in culture, showed that Lovastatin inhibited steroid induced fat specific gene expression and counteracted the inhibitory effects of steroids on osteoblastic gene expression. For the in vivo study, 83 adult chickens were used: 48 received methylprednisolone 3 mg/kg weekly via intramuscular injection (Group A). Fifteen received the steroid (as in Group A) plus Lovastatin 20 mg per animal per day orally (Group B). Ten chickens received Lovastatin only (Group C). Another 10 received no medication and served as the control group (Group D). Evidence of osteonecrosis was observed in specimens from Group A, including subchondral bone death and resorption, fat cell proliferation, and new bone formation. Conversely, sections from Group B showed less adipogenesis and no bone death. It is concluded that the bipedal chicken is a useful animal model for studies of osteonecrosis and that lipid clearing agents, such as Lovastatin, may be helpful in preventing the development of steroid induced osteonecrosis.