The aim of the present study was to compare selected markers of oxidative stress and the antioxidant system between groups of men aged 65 or more, differentiated by their level of physical activity. Thirty-one community-dwelling healthy, elderly men (mean age 73.4 +/- 6.1 years) with a good nutritional status participated in the study. The Caltrac accelerometer was used to estimate energy expenditure related to physical activity. Subjects were divided into two groups according to the criteria proposed by Bauman: less active (< 1600 kcal/week) and more active (> 1600 kcal/week). In all the men, plasma total antioxidant status (TAS), thiobarbituric acid reactive substances (TBARS) concentrations and hydrogen peroxide (H2O2) levels were determined. The reduced glutathione (GSH) content and glutathione peroxidase (GPx) activity in hemolyzed red blood cells were also measured. There were no significant differences in TAS, H2O2 concentrations and the activity of GPx between less and more active men. In the group of more active subjects, plasma levels of GSH were higher, while TBARS concentrations were lower compared with the group of less active men (p < 0.05). Negative correlation between GSH and TBARS levels was observed (r = -0.71; p < 0.01), and GSH concentrations positively correlated with level of physical activity (r = 0.63; p < 0.05). The results indicate that habitual physical activity can favorably affect antioxidant potential and prevent lipid peroxidation in healthy, elderly men.