Heterogeneous cation-exchange membranes differing in their binder poly(vinyl chloride) and ion-exchange resin ratios as well as the mesh size of the resin particles have been prepared by solution casting technique. The conductivities of such membranes in varying concentration of different electrolyte solutions such as HCl, NaCl, KCl, and CuCl2 have been measured. The membrane conductance values in conjunction with solution conductivities have been used for the estimation of isoconductance points. Considering the membrane as a combination of joint-gel phase and intergel phase, the volume fractions of the respective phases have been evaluated. With the help of isoconductance points, the electroconductivities of the joint-gel phase and counterion diffusion coefficient through that phase of the membrane in equilibrium with different electrolyte solutions have been found. The sequence of ionic mobilities and counterion diffusion coefficient through the Joint-gel phase is H+ > K+ > Na+ > Cu2+, while ion-exchange capacity of the joint-gel phase decreases as Cu2+ > K+ approximate to Na+ > H+.