In this paper the energetic optimization of a proton exchange membrane fuel cell integrated with a steam reforming system using ethanol as fuel is analysed. In order to obtain high hydrogen production, a thermodynamic analysis of the steam reforming process has been carried out and the optimal operating conditions has been defined. Moreover, the overall efficiency of the PEMFC-SR system has been investigated as a function of the fuel utilization factor and the effects of the anodic off-gas recirculation have been evaluated. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.