The modified Gouy-Chapman theory of the electrical double layer in which ion-core effects among the ions are neglected, but are taken into account in the ion-electrode interaction, is applied to the case of 1:1, 2:2, 1:2, and 2:1 electrolytes for both equal and unequal ionic diameters. At large charge densities on the electrode, the counterions dominate and the results approach those of a symmetric electrolyte. However, at small charge densities on the electrode, the effects of asymmetry are evident. In particular, for unequal ionic diameters, a nonzero potential can occur at zero charge on the electrode, even in the absence of specific adsorption. © 1983 American Institute of Physics.