We have considered the ion transport across a membrane with extended soft permeable interfaces (polar zones), placed in an aqueous solution, under short-circuit conditions. The existence of fixed charges and dipoles in these membrane interfaces has been taken into account. The membrane has been modeled as composed of three layers : an inner hydrophobic layer and two polar zones. Nernst-Planck＇s equation has been used for describing the ion transport. This paper continues our previous study, where we introduced the general model and analyzed the limit case of the internal hydrophobic layer as the rate-controlling step for ion transport (Langmuir 1996, 12, 4817). Here we have examined another limit case with the polar zones as the rate-controlling step for ion transport. The influence of the electrolyte concentration, the surface dipole density, and thickness of the polar zone on the total ion flux and permselectivity has been analyzed. It is shown that there are two significant differences with respect to the earlier considered limit case. On one hand, the steady-state condition leads to the build up of an additional space charge inside the polar zones, which influences considerably the ion transport. On the other hand, the membrane permselectivity exhibits a different variation with the electrolyte concentration. It is concluded that the analysis of permselectivity can help to find the rate-determining step in specific membrane systems.