The present study was designed to test the biocompatibility of a new vitamin E-modified multilayer membrane compared with highly biocompatible polysulphone dialyzer and acrylonitrile dialyzer. Thirty patients (mean age 53.2 ± 15.3 SD years; dialytic age 36 ± 5.6 months) were selected for the study. The study was divided into three periods of 6 months (phases A, B and C). In the first phase (from Jan. 1999 to June 1999) patients undergoing maintenance bicarbonate dialysis were randomly divided into three filter groups composed, respectively, of 10 patients: acrylonitrile group, polysulphone group and vitamin E-coated dialyzer group. In the phase B (from July 1999 to Dec. 1999) and in the phase C (from Jan. 2000 to June 2000), all three groups changed their own dialysis membranes. Vitamin E-coated dialyzer causes significant decreases in β<sub>2</sub>-microglobulin, ferritin and immunoglobulin G, a normalization of complement C3 and an increase of plasmatic vitamin E compared to other filters. In the VE group homocysteine decreases but not in a significant manner. In addition, this dialyzer seems not to influence lipid pattern and protein-energy malnutrition parameters. These results clearly show a positive effect of this new filter in influencing different biochemical parameters, perhaps saving vitamin E and reducing polymorphonuclear cell activation.