Sex and lifestyle factors are known to influence the oxidation of protein, lipids, and DNA. Biomarkers such as protein carbonyls (PC), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) have been commonly used in an attempt to characterize the oxidative status of human subjects. This study compared resting blood oxidative stress biomarkers, in relation to exercise training status and dietary intake, between men and women. Exercise-trained and sedentary men and women (with normal menstrual cycles; reporting during the early follicular phase) were recruited from the University of Memphis, Tennessee, campus and surrounding community via recruitment flyers and word of mouth. Participants were categorized by sex and current exercise training status (ie, trained or untrained). Each completed a detailed 5-day food record of all food and drink consumed. Diets were analyzed for kilocalories and macro- and micronutrient (vitamins C, E, A) intake. Venous blood samples were obtained at rest and analyzed for PC, MDA, and 8-OHdG. In the 131 participants (89 men, of whom 74 were exercise trained and 15 untrained, and 42 women, of whom 22 were exercise trained and 20 untrained; mean [SD] age, 24  years), PC did not differ significantly between trained men and women or between untrained men and women. However, trained participants had significantly lower plasma PC (measured in nmol . mg protein(-1)) (mean [SEM] 0.0966 [0.0055]) than did untrained participants (0.1036 [0.0098]) (P < 0.05). MDA levels (measured in micromol . L(-1)) were significantly lower in trained women (0.4264 [0.0559]) compared with trained men (0.6959 [0.0593]); in trained men and women combined (0.5621 [0.0566]) compared with untrained men and women combined (0.7397 [0.0718]); and in women combined (0.5665 [0.0611]) compared with men combined (0.7338 [0.0789]) (P < 0.05 for all comparisons). No significant differences were noted between any groups for 8-OHdG. Neither PC nor 8-OHdG were correlated to any dietary variable, with the exception of PC and percent of protein in untrained men (r = 0.552; P = 0.033). MDA was positively correlated to protein intake and negatively correlated to percent of carbohydrate and vitamin C intake, primarily in trained men (P < or = 0.03). In this sample of young healthy adults, oxidative stress was lower in women than in men and in trained compared with untrained individuals, particularly regarding MDA. With the exception of MDA primarily in trained men, dietary intake did not appear to be correlated to biomarkers of oxidative stress.