Data on the physico-chemical characterization and on the catalytic activity in CH4 combustion of BaFe12O19 and BaFexAl(12-x)O-19 samples (x = 1, 3, 6, 9) are reported. BaFe12O19 shows good catalytic activity in CH4 combustion, but does not possess the required thermal stability. It completely sinters upon calcination at temperatures higher than 1000 degrees C and deactivates both on increasing the calcination temperature and upon treatment at 900 degrees C under reaction conditions. The catalytic properties of this system completely degenerate upon calcination at 1300 degrees C. Deactivation seems to be related both to sintering and to a Fe3+ --> Fe2+ reduction involving limited metal amounts. Partial replacement of Fe ions with Al3+ ions improves the thermal stability of the Fe-containing systems. Upon calcination at 1300 degrees C BaFe6Al6O19 retains a surface area of 5 m(2)/g and shows a good activity in CH4 combustion.