The activity of magnesium oxide for catalytic combustion of methane was examined and the results were compared with experimental results for manganese-substituted barium hexaaluminate. The catalysts were calcined at temperatures up to 1 500 degrees C and the effects of temperature, space velocity and calcination temperature were examined. The catalysts were also characterized with BET and XRD. For magnesium oxide calcined at 1 100 degrees C the ignition temperature (T-10%) was decreased by 270 degrees C compared to the non-catalyzed reaction. For the same catalyst T-50% was measured to be 795 degrees C. The corresponding temperature for the hexaaluminate was 640 degrees C. The difference between the two catalysts decreased after calcination at 1 500 degrees C. For the magnesium oxide the influence of catalytically initiated homogeneous gas phase reactions was studied by varying the post catalytic volume of the reactor (and hence the residence time in the heated zone after the catalyst). It was shown that these catalytically initiated homogeneous gas phase reactions are significant for the methane conversion.