A membrane charge is one of the most important factors that affects the permeation of ions through the membrane. For amphoteric membranes such as inorganic membranes, the membrane charge depends on the pH and the electrolytes in the bulk solution. In this paper, we theoretically discuss the permeation of ions through the amphoteric membrane using the advanced amphoteric membrane model. In this model, the membrane charge is determined by the dissociation of the amphoteric membrane material as well as the selective adsorption of ions. We assumed that the system was in the steady-state and there was no volume flow. We also assumed that no ions were adsorbed selectively in order to clearly show the effect of the dissociation of membrane material. As a result of the discussion, it was theoretically predicted that the flux through the amphoteric membrane was maximized with the pH. It is, therefore, possible to select the best condition for a large flux by adjusting the pH of the bulk solution. (C) 2003 Elsevier Science B.V. All rights reserved.