Mathematical model and numerical method are developed to analyze the operation of a coupled methane steam reformer. The reformer operates in co-current mode of endothermic (steam reforming) and exothermic (fuel oxidation) departments. The exhaust anode gas of a fuel-cell battery containing hydrogen is used as fuel. Two-dimensional, two-temperature mathematical model of monolith is used to describe processes in exothermic and endothermic departments of the reformer. Calculation results were compared with experiments. The agreement between the modeling and the experimental results is rather good. The model analysis points out that the considered reactor design has high parametric sensitivity, there is a probability of arisen of a hysteresis with points of ignition and extinction. (c) 2007 Elsevier B.V All rights reserved.