The catalytic production of hydrogen by steam reforming of methanol was investigated using samples of copper oxide supported on alumina (Cu/Al2O3) and promoted with cesium (Cu-Cs/Al2O3). The effects of cesium content and reaction temperature on the catalytic activity were investigated. The Cu-Cs/Al2O3 catalysts exhibited higher activity and stability as compared to the undoped ones. The catalyst containing 2 wt% of cesium was the most active and at 300 degrees C the methanol conversion reached 94 mol% and the hydrogen selectivity 97 mol% with no detectable formation of CO. After an ageing treatment at 400 degrees C, methanol conversion was still close to 100% with the cesium-doped catalyst, while the undoped catalyst drastically deactivated. X-ray powder diffraction (XRD) and XPS measurements indicate that cesium prevents the reduction of copper oxide into metallic Cu, by the hydrogen produced, and inhibits the formation of CuAl2O4 spinel upon thermal treatment. (c) 2006 Elsevier B.V. All rights reserved.