We investigated the effects of red wine on blood antioxidant potential in an attempt to elucidate molecular mechanisms concerning the possible protective role of red wine in atherosclerosis. Volunteer subjects in the study group consumed a standard meal and drank red wine (5 mg/kg) while controls consumed the same meal and drank water. Over 4 1/2 hours, blood samples were taken, and malondialdehyde (MDA) and antioxidant potential (AOP, obtained from MDA levels before and after superoxide radical attack) values were measured in the plasma and erythrocytes. We found that AOP values of plasma and erythrocyte samples from the study group were at their highest after 1 1/2 hours and then declined to basal values at 4 1/2 hours. There were no statistically significant differences between the basal AOP values of the study group and the control group. With regard to MDA levels, gradual increases were seen in the plasma of the control group during the 3 hours after food, but no changes were seen in the plasma of the study group in this period. Although there were increases in erythrocyte MDA levels of both groups over 3 hours, the MDA production rate was significantly higher in the control group. Our results suggest that red wine causes significant increases in AOP values of plasma and erythrocytes, which may prevent cellular peroxidation reactions and lessen atherosclerotic complications through inhibition of LDL.