The notion that oxidation of lipids and lipoproteins may contribute to the pathogenesis of atherosclerosis is supported by a large body of evidence. It is hypothesized that dietary antioxidants may help prevent development and progression of atherosclerosis. The available evidence helps substantiate this hypothesis but is not yet conclusive. The results of several ongoing large randomized intervention trials will provide valuable information about the efficacy and safety of supplemental dietary antioxidants in prevention of atherosclerosis.