Catalytic activity for CH4 oxidation and resistance to SO2 poisoning were tested for three LaCoi-xFeXO(3) prepared by reactive grinding. The catalysts prepared by this method showed well-crystallized perovskite structure and various specific surface areas. The activity in CH4 oxidation correlates well with BET specific surface area. TPDO experiments showed very large quantities of desorbed beta-oxygen that could not be correlated to the activity for CH4 oxidation. Resistance to sulfur poisoning in the same reaction was tested at 500 degreesC with 25 ppmv SO2 added to the feed. Two steps were distinguished during the poisoning reaction. The first one followed an exponential decrease of conversion versus time. The time to reach the end of this step was shown to be directly proportional to the specific surface area. In this step, deactivation was found to be reversible. During regeneration, some sulfur species were found to desorb from the catalyst. The second step was found to be a linear diminution of conversion with time. The slopes of these lines were found to be the same for the three catalysts. A total of 860 h is necessary to deactive the catalyst with the higher specific surface area, and the quantity of sulfur accumulated in the catalyst was found to vary linearly with the poisoning time. XRD showed significant conversion of the catalyst into La-2(SO4)(3), Co3O4, and iron oxide. The complex poisoning behavior is discussed and associated to the observed differences in the catalyst morphology.