Catalytic performance and characterization of Pd/Ni0.2Mg0.8Al2O4 were investigated in oxidative steam reforming of methane under atmospheric and pressurized conditions. Pd/Ni0.2Mg0.8Al2O4 showed much higher methane conversion under high partial pressure of steam, where Ni0.2Mg0.8Al2O4 lost the reforming activity because the Ni species was oxidized under atmospheric pressure. In addition, the addition of Pd on Ni0.2Mg0.8Al2O4 was effective to improve the stability and resistance to coke formation in oxidative steam reforming of methane under pressurized conditions. On the other hand, the formation of Pd-Ni alloy over Pd/Ni0.2Mg0.8Al2O4 was confirmed from the characterization results of TPR, TEM, EXAFS and FTIR, and this can contribute to high catalytic performance of Pd/Ni0.2Mg0.8Al2O4 (C) 2007 Elsevier B.V. All rights reserved.