On-board methanol reforming is an attractive alternative to direct hydrogen storage for solid polymer fuel cell (SPFC) powered vehicles, due to the increased volumetric energy storage density of methanol. Unfortunately, carbon monoxide is always produced during the reforming reaction. CO rapidly de-activates the platinum electro-catalyst in the fuel cell and must be reduced to levels typically less than 20 ppm. In this paper, the development of a precious metal based catalytic CO oxidation reactor developed by the Fuel Cell Research Group at Loughborough University is reported. A simplified simulation model has also been developed, based upon measured catalyst activity and CO oxidation selectivity. Experimental results from reactor studies show that CO concentrations can be reduced from a typical steam reformer output of 7000 ppm input to less than or equal to 15 ppm in the presence of approximately 75% hydrogen. Experimental results have shown good agreement with the simulation model. (C) 2000 Elsevier Science S.A. All rights reserved.