This paper presents the results of a parametric study conducted with a previously described three-dimensional, non-isothermal model of a polymer electrolyte membrane (PEM) fuel cell. The effect of various operational parameters such as the temperature and pressure on the fuel cell performance was investigated in detail. It was found that in order to obtain physically realistic results experimental measurements of various modelling parameters were needed. The results show good qualitative agreement with experimental results published in the literature. In addition, geometrical and material parameters such as the gas diffusion electrode (GDE) thickness and porosity as well as the ratio between the channel width and the land area were investigated. The contact resistance inside the cell was found to play an important role for the evaluation of the impact of such parameters on the fuel cell performance. The results demonstrate the usefulness of this computational model as a design and optimization tool. (C) 2003 Elsevier B.V. All rights reserved.