A steady-state, two-dimensional model of the cathode of a polymer electrolyte membrane fuel cell (PEMFC) with interdigitated gas distributor is formulated with the intention of studying the effects of various operating parameters on its performance. The model describes the fluid dynamics of reactant gases and gives an insight to their distribution in the electrode. The model is verified with published data [J. S. Yi and T. V. Nguyen, J. Electrochem. Soc., 146, 38 (1999)], but an error has been detected in the data. This work corrects the error, and the results are presented. The effect of changes in electrode permeability, thickness, and shoulder width are then studied. It is observed that changes in permeability, ranging from 10(-8) to 10(-13) m(2), has little impact on the cell performance. Both increasing the electrode thickness and the shoulder width result in poorer performance due to greater resistance to flow. In addition, results show that liquid water tends to form near the outlet of the electrode when the current density is greater than 1.0 x 10(4) A m(-2). The 2D model is then extended to a 3D one to determine the flow distribution in a fuel cell for an interdigitated gas distributor. A comparison in performance is made with this 3D model between an interdigitated/ conventional gas distributor and it is found that an interdigitated gas distributor does improve cell performance over a conventional gas distributor. (c) 2005 The Electrochemical Society.