A series of Ni-Ce catalysts supported on illite clays with different amount of cerium were tested with respect to autothermal reforming of methane at 800°C using a GHSV = 60000 mL.g-1.h-1. The addition of cerium was found to enhance the catalyst surface area as result of meso-porosity development. Furthermore, the nickel particles size are lowered in the presence of Ce, decreasing the Ni° average size from 34.2 for 10Ni to 16.3nm for 10Ni15Ce. The best catalytic activity and stability were obtained using the catalyst with 15wt% of Ce, which was attributed not only to the redox properties of cerium but also to the better nickel dispersion. On the other hand, the addition of oxygen in the gaseous reactant feed, under the used experimental condition was found to play a key role since the amount of carbon deposition is significantly reduced regardless the catalyst composition.