The reaction of the partial oxidation of methane was investigated over Ni/La2O3 catalysts prepared by impregnation. Two different reactors were used, a perfectly jet-stirred reactor and a fixed-bed reactor. The influences of nickel content, calcination temperature, reaction temperature, residence time, and contact time were investigated. Mechanistic information was derived from the comparison of the results obtained in both reactors. Characterization techniques such as X-ray diffraction, temperature-programmed oxidation, temperature-programmed reduction, and transmission electron microscopy were used to assess the state of the catalyst prior to and after the reaction.