Background: Oxidative stress is an important risk factor for the development and progression of several complications in hemodialysis patients. The aim of this study was to evaluate the effects of two different dialysis membranes on oxidative stress and selenium status. Methods: Forty long-term dialysis patients and 20 age-matched healthy controls were enrolled into our study. Serum malondialdehyde (MDA) and selenium (Se) concentrations, and glutathione peroxidase (GSH-Px) activities were determined before and after hemodialysis (HD) using a hemophan (H) or a polysulfone (PS) membrane. Results: MEA levels in the HD patients were significantly higher than those in the control group (p < 0.001). GSH-Px activity and selenium concentrations were significantly lower in HD patients compared to the control group (p < 0.001). MDA levels were significantly increased (p < 0.05); GSH-Px activity and selenium concentrations were significantly reduced (p < 0.001) in the PS membrane group compared to H membrane group after HD. Conclusions: Comparing with H membrane, PS membrane caused more oxidative stress and lower levels of Se in HD patients. (C) 2004 Elsevier B.V. All rights reserved.