Crosslinked sulfonated ion-exchange blend membranes have been produced via a new crosslinking process. The blends have been obtained from mixing PSU-SO3H and PSU-SO2H in different sulfinic acid/sulfonic acid relations in N-methyl pyrrolidone. The crosslinking process consists of the disproportionation between SO2H groups which occurs during membrane formation. These membranes have been characterized in terms of ion-exchange capacity, ion-resistance, swelling, ion-permeability, and ion-permselectivity. Some of the membranes have been applied to electro-membrane processes, as electrodialysis, and PEM fuel cells (PEM=polymer electrolyte membrane), The advantages of the sulfinate disproportionation crosslinking process are : (i) the crosslinking process is easy to do; (ii) the ion-exchange capacities of crosslinked membranes and thus their ionic resistance, swelling and permselectivity can be varied in a broad range. The crosslinked blend membranes show good thermal stabilities and are suitable for application in electrodialysis. Although the property profile of the blend membranes still has to be improved further, it is demonstrated that they are in principle suitable for application in PEM fuel cells.