Models for mass transport inside a porous SOFC anode were developed based on Fick's model (FM), the dusty-gas model (DGM) and the Stefan-Maxwell model (SMM) to predict the concentration overpotential. All models were validated with experimental data for H-2-H2O-Ar and CO-CO2 systems. The effect of pore size on all model predictions was discussed. It was concluded that the dusty-gas model is the most appropriate model to simulate gas transport phenomena inside a SOFC anode. However, this model requires numerical solution, whereas Fick's and Stefan-Maxwell's do not. It was found that the SMM, rather than the FM, is a good approximation of the dusty-gas model for H-2-H2O system, except in the case of high current density, low H-2 concentration and low porosity, where only the DGM is recommended. For the CO-CO2 system, there is no simple rule for selecting an alternate model to DGM. Depending on the CO concentration, porosity and current density, the FM or the SMM could be used. The only restriction is for small porosities where only the DGM should be used. This paper also demonstrated that only the DGM is recommended for a multicomponent system (H-2-H2O-CO-CO2). (C) 2003 Elsevier Science B.V. All rights reserved.