Autothermal reforming of methane, combining steam reforming and partial oxidation was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/ZrO2/ Al2O3 catalysts, in the temperature range of 400-900 degrees C. The PUZrO2/Al2O3 catalyst was found to be the most active and stable at 800 degrees C due to the higher resistance to coke formation. The reaction occurs in two simultaneous stages: total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O-2 conversion of 100 % starting from 450 degrees C. The addition of O-2 to the feed increases methane conversion and the catalyst stability, decreasing the H-2 and CO yields due to the enhancement of methane combustion. By manipulating the O-2/CH4 ratio of the feed it is possible to achieve the H-2/CO ratio that is optimal to the GTL processes. (c) 2004 Elsevier B.V. All rights reserved.