The aim of the paper is the experimental analysis, through a statistical methodology, of the effects of the main stack operation independent variables on the cogenerative performance of a PEMFC stack. The tests have been performed on a ZSW 0184 stack of 800W using the GreenLight GEN VI FC Test Station. The statistical methodology used for the experimental data analysis has been the factorial design: we have analysed the significance of the main operation independent variables (anode and; cathode flow dew point temperature; cathode flow stoichiometry) considering their single and combined effects on the electric and thermal power which could be recovered from the stack. The results show that the anode flow inlet temperature and the cathode flow dew point temperature have no significant effect at every level of current density both for electric and thermal power. At the same time, the cathode flow inlet temperature has a significant positive effect on the electric power at every level of current density, and especially the cathode flow stoichiometry shows significant positive effects on the electric power and negative effects on the thermal power recovered from the stack. (c) 2005 Elsevier B.V. All rights reserved.