The grinding operation of La0.8Sn0.2MnO3 (LSM) powder by a vibration mill has been carried out with the intention of giving a higher surface area and a good thermal stability. The specific surface area of the LSM powder increased with operation time and reached up to 34 m(2) g(-1) for 350 h. XRD measurement and chemical analysis showed that during the grinding operation, the crystal structure of the LSM powder was kept and that the extent of the contamination was negligibly small. In CH4 oxidation at 400 degrees C and N2O reduction at 450 degrees C over the ground LSM powder, both conversions were raised proportional to the increasing specific surface area. Furthermore, the thermal stability of the ground LSM powder was improved by grinding it together with CeO2 powder. The fine dispersion of CeO2 particles around the LSM particles effectively depressed the sintering of the LSM powder at elevated temperatures.