A numerical procedure is introduced to calculate the profiles of ion densities and electric fields in polymer electrolytes with blocking electrodes. For low electric potentials the numerical results are in agreement with Jaffe's approximate analytical solutions. In contrast to the analytical solution the numerical procedure is also suitable for high electric potentials at which the relation between dielectric polarisation and electric potential becomes strongly nonlinear. Furthermore, the temporal development of ion distributions can be modelled after the application of a voltage step or under other transient voltages. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.