Supported nickel catalysts were prepared by impregnation of La2O3, MgO and ZrO2 substrates and tested in the partial oxidation of methane to synthesis gas at atmospheric pressure. Nickel interacted strongly with La2O3 forming a deficient LaNiO3-delta perovskite structure upon calcination. Upon reduction at 973 K, the Ni/La2O3 catalysts that resulted were highly active and selective for syngas production. By contrast, a separate and readily reducible NiO phase was formed on the ZrO2 support. Because the interaction of metallic nickel particles on ZrO2 is weak, the catalysts underwent deactivation by sintering of metal particles during on-stream operation as confirmed by photoelectron spectroscopy. The relatively high activity of the Ni/MgO systems was associated with the formation of a highly stable cubic Ni-Mg-O solid solution, in which nickel remains highly dispersed during the methane partial oxidation reaction.