['To ascertain whether indicators of oxidative damage to lipids (malondialdehyde (MDA)) and proteins (protein carbonylation) are biomarkers of frailty, after adjusting for age, sex, and other possible confounders.', 'Cross-sectional cohort study.', 'Community.', 'Toledo Study for Healthy Aging participants (N = 742, aged 65-95), classified as frail (n = 54), prefrail (n = 278) and nonfrail (n = 410) according to the Fried criteria.', 'Blood plasma was obtained using centrifugation (1,500 G, 15 minutes) and immediately frozen at -80°C. Plasma lipid peroxidation was determined by measuring the MDA formed from lipoperoxides using high-performance liquid chromatography and protein carbonylation was measured using Western blot.', 'Age- and sex-adjusted levels of lipoperoxides (measured as MDA) and protein carbonylation in plasma proved to be related to frailty, even after including possible independent confounders.'] Is oxidative stress related to frailty , not to age or sex , in a geriatric population : lipid and protein oxidation as biomarkers of frailty?