Abstract To design intelligently such membrane devices as fuel cells, batteries, and sensors, an understanding of the membrane's ion-transport characteristics is necessary. In ion-exchange membranes, these characteristics are dependent on the electric-potential profile generated in the membrane pore primarily by electrostatic interactions between fixed-charge species of the membrane and mobile ions within the membrane pores. In this work, molecular-level models for the solvation of ions, alignment of solvent dipoles, and adsorption of ions onto the pore surfaces of the membrane are combined with Poisson's equation for simulation of the electric potential within a membrane pore. The incorporation of ion solvation with a variable solvent dielectric constant is shown to increase significantly the value of the electric potential in the vicinity of the pore wall. The dielectric constant near the pore wall decreases by over an order of magnitude. Unlike previous analyses, the model contains ion-specific parameters, and the computed potentials are dependent on the electrolyte cation and anion species.