A combined mass and heat transport model has been developed in the case of an anode-supported solid oxide fuel cell (SOFC) fed with methane with special attention given to the description of electrochemical polarizations. The mass balance of gases within the porous anode has been described in terms of gas diffusion and both chemical and electrochemical reactions. The kinetic reactions and the temperature field have been expressed, one depending on the other and reciprocally. The main result is a rather small temperature gradient (2 degrees C cm(-1)) obtained at 800 degrees C with S/C=1 in classical operating conditions. The influence of thermal, kinetic, and microstructure parameters on the current density and temperature gradient over the whole cell has been studied. In this sensitivity analysis, the kinetic constant of the steam reforming reaction is shown to be the most efficient parameter on the cell performance. (c) 2005 The Electrochemical Society. All rights reserved.