Simulations were performed of a proton exchange membrane fuel cell (PEMFC) in which the membrane electrode assembly (MEA) was deflected such that the adjacent shoulders of the channel assembly were at different heights. The effect on cell performance of varying the MEA deflection was examined while maintaining the same reacting area and boundary conditions at high operating current densities. A three-dimensional, non-isothermal model was employed with a single straight channel. Both humidification and phase transportation were included in the model to obtain the total water management for systems operating at different current densities. The cell performance was found to increase significantly at a certain, optimal deflection. The cathode overpotential decreased significantly with increasing MEA deflection as the reactants became more evenly distributed over the reacting area. A preliminary investigation of the deflection behavior of different MEA materials under clamping pressures taken from the literature indicated that MEA materials can be deflected up to the optimal deflection condition provided the clamping pressure is within the elastic limit of the gas diffusion electrode (GDE). (C) 2008 Elsevier Ltd. All rights reserved.