A full three dimensional PEM fuel cell model is developed, which considers not only the rib resistance to the species but both the single and two phase flow and transport in the gas channels and diffusers at both the anode and cathode sides of the PEM fuel cell. Two sets of boundary conditions, one for a conventional flow field and the other for an interdigitated one, are presented. A detailed discussion of the numerical techniques for the PEM fuel cell model is given with a flow diagram to provide an overview of the solution procedure using the FORTRAN language. A rigorous validation method is used to show good agreement between our predicted results and the experimental data. (C) 2003 Elsevier Ltd. All rights reserved.