Enhanced oxidant stress plays a pivotal role in the pathogenesis of several conditions such as atherothrombosis, cancer and neurodegeneration. The availability of reliable assays of isoprostanes in biological fluids has prompted clinical investigations into the pathophysiological role of lipid peroxidation in cardiovascular disease. Established risk factors for coronary heart disease have been associated with enhanced oxidant stress, leading to increased lipid peroxidation and non-enzymatic formation of bioactive isoprostanes. These risk factors include diabetes mellitus, hypercholesterolemia, obesity and hyperhomocysteinemia. Clinical studies support the hypothesis that enhanced lipid peroxidation may contribute, at least in part, to persistent platelet activation.