This paper presents a numerical model for a planar solid oxide fuel cell (SOFC) with mixed ionic-electronic conducting electrodes. Transport of positive or negative charges, which takes place in the direction of down- or up-gradient electric potential, respectively, within the composite electrodes and through the electrolyte membrane, is mimicked by making use of an algorithm for Fickian diffusion in the commercial software. The output cell voltage, which is the potential difference between the two current collectors, is fixed at a given value. The coupled equations describing the conservation of mass, momentum and energy and the chemical and electrochemical processes are solved using the commercial package Star-CD, augmented with subroutines developed in-house. Results for the concentration of chemical species and the distributions of temperature and current density in an anode-supported SOFC with direct internal reforming are presented and discussed. The potential for using this model as a general numerical tool to study the impact of the detailed processes taking place in SOFCs is discussed. (c) 2008 Elsevier Ltd. All rights reserved.