An empirical voltage-current model is normally used to replicate the performance of a fuel cell under specific conditions. It is also a powerful toot that can be used to simplify the analysis of a complex problem. In this study, an improved empirical voltage-current model was proposed and subsequently used to demonstrate the effect of carbon powder loading and PTFE content on the overall overpotential of fuel cells with carbon-filled gas diffusion layer (CFGDL). This proposed empirical equation was proved to be more accurate than those available in the literature for CFGDL, as each parameter in the model has respective physical significance. In this model, the gas concentration losses were represented by a linear change of current over the entire range of current densities and a corrected exponential change of current term for cases only occurring at high current densities. Non-linear regression was applied to determine the parameters in the empirical equations. A series of statistical evaluations, which included calculation of standard deviation and 95% confidence interval of the parameters, served in model identification and verification. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.