Abstract: A dialyzing membrane, especially for hemodialysis, formed as a hollow fiber, tubular foil or flat sheet by regeneration of cellulose from a cuprammonium solution, the membrane comprising at least two firmly adhered cellulosic layers including at least one dialyzing layer consisting essentially of a semipermeable regenerated cellulose and at least one adsorbent layer consisting of said regenerated cellulose containing embedded therein fine particles of an adsorbent material in an amount of up to 95% by weight with reference to the dry weight of the adsorbent layer, preferably 1 to 90% and especially 20 to 70% by weight, when the adsorbent layer is part of a hollow fiber structure.