The transport properties of the membrane and the related dissipative phenomena significantly affect the performance of polymeric electrolyte membrane fuel cells. In this work the transport mechanisms taking place inside the membrane and the interaction of these with the adjacent electrodes will be analysed in some detail to gain a better understanding and control of cell performance and particularly of open-circuit voltage losses, which can be anything up to 30% of the effective voltage of an operating cell, as such an understanding could lead to significant technological improvements. Here we present an analytical and interpretative description to try to identify the irreversible electrode phenomena under open-circuit conditions in terms of a dissipative steady-state and related "parasitic currents". (c) 2006 Elsevier B.V. All rights reserved.