Ion exchange membranes were prepared by simultaneous radiation grafting of styrene into FEP films and subsequent sulfonation, Divinylbenzene was used as crosslinker in the grafting medium. The distribution of polystyrene grafts across the membrane matrix was determined by microprobe measurements. It was observed that for low levels of grafting such as 13%, crosslinked membranes had a better homogeneity in graft distribution across its matrix as compared to the non-crosslinked ones. The latter showed a much higher concentration of grafts at the surface than in the middle of the film. The membrane characteristics, such as swelling and specific resistivity as a function of the degree of grafting and crosslinking were evaluated. Membranes showed a sharp decrease in the resistivity up to similar to 25% grafting, beyond which the decrease was not significant. The higher the crosslinker content, the higher was the ionic resistivity. A relation between the degree of grafting and membrane properties, such as degree of swelling and specific resistivity as a function of the crosslinker content was established.