Abstract: Membrane-electrode assembly consisting of a cationic exchange membrane which contains fluorine (made of hydrolyzed copolymer of tetrafluoro-ethylene and vinyl ether which contains perfluorosulfur with PE=900-1300) and porous layers of electrode material (made of electrocatalyst), inactive electroconductor material and fluoropolymer agglutinating material arranged on both surfaces of the cationic exchange membrane. The cationic exchange membrane which contains the fluorine is made of hydrolyzed copolymer of tetrafluoroethylene with vinyl ether which contains perfluorosulfur, having a crystallinity grade between 2 and 8%; porous layers of the electrode material are obtained which have a porosity comprised between 40 and 70% and decreasing in the direction of the cationic exchange membrane surface with a porosity gradient from 5 to 15% par 1&mgr;. Said membrane-electrode assembly is used in fuel cells, in water electrolysis and in other electrochemical process.