Several years ago we hypothesized that products of lipid and lipoprotein oxidation may contribute to pathophysiology of osteoporosis (F. Parhami, Curr. Opin. Lipidol. 8 (1997) 312), and that their effects on artery wall and bone cells may explain the parallel development of osteoporosis and atherosclerosis in the same subjects (R. Boukhris, JAMA 219 (1972) 1307; M.A. Frye, Bone Miner. 19 (1992) 185). Since then, new evidence has accumulated in support of this hypothesis and its possibility is being further tested by investigators in both vascular and bone fields (A.D. Watson, J. Biol. Chem. 272 (1997) 13597). This review will summarize the evidence to date that support the role of oxidized lipids in osteoporosis, and will address some of the issues that need further examination in order to establish whether hyperlipidemia and susceptibility to lipid oxidation may serve as risk factors for osteoporosis.