The aim of this study was to evaluate whether hydroperoxide levels, an index of oxidative stress, predict cardiac and total death in patients with cardiovascular disease. Serum hydroperoxide levels were measured in 157 consecutive inpatients, followed during a mean follow-up of 20+/-0.3 months. Elevated oxidative stress resulted in an independent predictors for cardiac death, suggesting that hydroperoxide evaluation could provide an adjunctive estimate in the evaluation of prognosis in the cardiovascular clinical setting.