Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al2O3 Supports that were either unpromoted or promoted with CeO2, ZrO2 and CeO2-ZrO2. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO2 and/or ZrO2 showed that the variations induced in the Al2O3 by the addition of CeO2 and/or ZrO2 alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO2-ZrO2, improved catalytic activity by increasing the H-2 yield and the CO2/CO and the H-2/CO values while decreasing coke formation. This results from the addition of ZrO2 into CeO2. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.