The compatibility of ionomer/polymeric acid blends has been studied for polymer pairs consisting of sodium salts of sulfonated polystyrene and methyl methacrylate-methacrylic acid copolymer using dilute solution viscometry. The intrinsic viscosities of the blends, prepared in three different weight fractions (25, 50 and 75%) using the solution-blending technique, were measured in two solvents with different polarities : dioxane (epsilon = 2.24) and tetrahydrofuran (epsilon = 7.26). The degree of compatibility of the blends was characterized using the ab parameter. Results show that the percentage sulfonation, temperature and polarity of the solvent all affect the miscibility.