The aim of this study was to compare the oxidant and antioxidant systems of patients with rheumatoid arthritis (RA) with those of healthy individuals as recent findings suggested that oxidative stress could be a component of the etiology of RA. Serum levels of malondialdheyde (MDA), vitamins A, E and C and activity levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in erythrocytes from 20 patients with RA and 20 healthy controls were used. They found a higher oxidative stress status and lower antioxidant status in patients with RA compared to healthy individuals, probably due to lipid peroxidation.