Ultrafiltration membranes were prepared from epoxidized polysulfone by the conventional phase separation procedure. For epoxidizing, the polymer was first lithiated and a reaction followed with glycidyl-4-oxohexylether providing an eight atomic spacer. The reaction of the epoxy group with N-containing substituents was performed heterogeneously using the ready membranes. The stability of the substituted membranes is visible by the fact that they are reacted under reflux conditions for 24 h. The reagents were trimethyl amine, diethylamine, n-butyl amine, and tauric acid. Thus, positively charged, negatively charged, and neutral membranes were obtained. The membranes were characterized via ultrafiltration using dextran solution as well as human albumin solutions. In addition, the streaming potential was measured in the presence and absence of the protein. By these measurements the obviously neutral membranes were surprisingly identified to be positively charged. This is related to subsequent reactions of the spacer-bonded epoxy groups with the amino groups.