A new method for preparing heterogeneous ion-exchange membranes was developed. It was found that application of an ac electric field during curing of the polymeric matrix resulted in the agglomeration of the ion-exchange particles in long linear chains extending across the membrane. As a result, the percolation threshold for ion conductance was reduced to values more than three to four times smaller than those for membranes with randomly distributed particles. The effect of ordering the particles on the membrane conductivity, swelling properties, ion-exchange capacity and permselectivity is studied. The advantages of the ordered membranes in electrodialysis and fuel cell applications are discussed. The experimental and theoretical aspects of this work were inspired through discussions with Prof. Ora Kedem. (C) 2004 Elsevier B.V. All rights reserved.