Abstract: A biocompatible dialysis membrane for hemodialysis in the form of flat sheets, tubular sheets or hollow filaments is disclosed. The dialysis membrane comprises a mixed polysaccharide ester of acetic acid, and/or propionic acid and/or butyric acid and has a structure represented by the formula ##STR1## wherein Cell denotes the skeleton of the polysaccharide molecule without hydroxyl groups; a, b, p, and s are numbers wherein s is a maximum degreee of substitution and the following equations are satisfied: ##EQU1## with the provision that, if a=0, then p and b must be greater than 0 and, if p or b=0, then a must be greater than 0.