Renal failure is accompanied by oxidative stress, which is caused by enhanced production of reactive oxygen species (ROS) and an impaired antioxidant defense. We studied 73 hemodialysis (HD) patients (39 males and 34 females) aged 24-75 years; the patients were randomized into two subgroups according to the type of hemodialysis membrane (35 patients were dialyzed on cellulose and 38 patients on polysulfone F7/F9 membrane dialyzers) and we assessed their antioxidant and lipid peroxidation status levels. The total antioxidant status (TAS) levels including whole blood levels of malondialdehyde (MDA) and glutathione (GSH); glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) activities were measured, before and after hemodialysis. The MDA levels significantly increased 52.0% and 16.9% post dialysis among the cellulose and the polysulfone dialyzer users, respectively, (P<0.05). The TAS levels significantly decreased, 22.0 and 16.5% in the cellulose and polysulfone dialyzer users, respectively, (P<0.05). The erythrocyte SOD activity decreased 25.1 and 19.1% in the cellulose and the polysulfone dialyzer users, respectively, (P<0.05). The GSH concentrations, post dialysis, decreased 49.9 and 6.8% in the cellulose and polysulfone dialyzer users, respectively, (P<0.05). In contrast, the erythrocyte activity of CAT, post dialysis, increased 15.0 and 37.3% in the polysulfone and the cellulose dialyzer users, respectively, (P<0.05). We conclude that the type of the dialysis membrane affects the oxidative status after HD with possible consequences on patient morbidity and mortality.