Abstract In fuel cells, in particular hydrogen-oxygen fuel cells with end plates 2, 6, an anode and a cathode electrode 3 and 5, both of which are in close contact with the surfaces of a hydratized, ion-exchanging membrane 4 which is arranged between these electrodes, and devices for supplying fuel gas to the anode 3 and an oxidizing (oxidant) gas to the cathode 5, there is the problem of the membrane drying out. In order to avoid this, the invention proposes that the membrane 4 be provided with micropores, the majority of which have a size of 0.001 micrometres to 1 micrometre, and/or is filled with porous particles, for example asbestos fibres, kaolin or the like, whose size is 0.01 micrometres to 10 micrometres. <IMAGE>