Abstract The effect of perfluorinated sulphocation-exchange membrane conditioning on their hydrophilic and electrotransport properties was studied. Exchange capacity and water content of MF-4SC membranes having been exposed to conditioning were determined by different chemical techniques. The estimated values were compared to the same characteristics after thermal pre-treatment by sequent boiling in hydrogen peroxide, water, acid and water. Dependences of electrical conductivity, diffusion and electro-osmotic permeability upon sodium chloride concentration were determined for MF-4SC, Nafion-115 and -117 provided that the conditioning techniques varied. Consistent increase of the electrotransport membrane characteristics due to the water content increase and water energy state alteration after the membranes were thermally treated was established. It was shown that MF-4SC, Nafion-115 and -117 conditioning by this method leads to formation of ion-conducting polymeric membranes identical in the structure and transport properties.