The effect of Pt addition to NiO-MgO solid solution catalysts on the performance in oxidative steam reforming of methane was investigated. In the oxidative reforming of methane, Pt/NiO-MgO gave much higher methane conversion than NiO-MgO and Pt/MgO, especially under short contact time (low W/F: W = catalyst weight, F = total flow rate). Although the effect of Pt was not clear in temperature program reduction profiles, the additive effect of Pt is remarkable in oxidative reforming of methane in term of catalyst activation. In the case of PtNiO-MgO catalysts, even when the H-2 reduction pretreatment was not done, the catalyst can be activated at a temperature higher than 773 K with a reactant gas including methane, steam, or oxygen. This behavior is related to the methane combustion activity. The order of the activity was as follows: Pt/NiO-MgO >> Pt/MgO > NiO-MgO. High combustion activity is related to methane activation ability, and this can make the catalyst activation and reduction easier. (c) 2005 Elsevier B.V. All rights reserved.