Catalytic autothermal reforming of methane was studied over a commercial nickel catalyst as a function of feed flow rate, feed composition and oven temperature. Temperature profile of the catalyst bed was measured by IR thermography and product composition was measured with a continuous gas analyzer. The effect of water addition on product composition and catalyst temperature profile was investigated in two different ways: by keeping oven temperature constant and by adjusting oven temperature in order to achieve the same maximum temperature in the catalyst bed. Temperature distribution in the catalyst was measured and, for each operating condition, the fraction of catalyst above a limiting value for deactivation and below a limiting value for coke formation was quantified. These information were coupled with data of methane conversion and hydrogen production, to identify a region of favourable reactor operating conditions, in the plane AIR/CH4-H2O/CH4. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.