In order to achieve a good activity with respect to methane combustion, a good route would be via catalysts incorporating transition metals. For devices operating at high temperatures, such as gas turbines, substituted hexaaluminates present the advantage of good thermal stability when compared to impregnated For the purpose Al 2 O 3 . of this study, manganese-substituted hexa-aluminates were prepared either by the sol-gel method or by carbonate precipitation. Surfaces were analysed by soft x-ray emission, namely low-energy electron-induced x-ray spectroscopy (LEEIXS), and by photoelectron spectroscopy, namely x-ray photoelectron spectroscopy. The results on samples incorporating increasing amounts of manganese show the existence of an upper limit to the number of atoms substituted at the catalyst surface. This limit is about 2.7 manganese ions per unit cell, for samples prepared either by the sol-gel or by the carbonate precipitation technique and then calcinated at 1200 ÄC. The interpretation of the Auger parameter variations shows that the relative amount of Mn in oxidation state III increases when the surface amount of Mn increases, as well as with the Mn substitution level. This fact can be related to an increased activity for methane conversion.