The simultaneous removal of carbon particulate and NOx has been studied over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution of metal into A- or B-site of perovskite oxide. In the LaCoO3 catalyst, the partial substitution of Cs into A-site enhanced the catalytic activity in the combustion of soot particulate and NO reduction. In La1-xCsxCoO3 catalysts, the ignition temperature of carbon particulate decreases with increasing x values and shows almost constant values at substitution of x > 0.2 and NO conversion also shows the similar tendency. In the Cs-substituted oxide, the ignition temperature of carbon particulate slightly decreased in the order Co > Mn > Fe of B-site metal cation but NO conversion showed almost similar values. With increasing NO concentration, NO conversion decreased but the ignition temperature moved to high temperature when the NO concentration was higher than 1000 ppm. The carbon particulate played an important role on the reduction of NO, but NO had little effect on the oxidation of carbon particulate. (C) 2000 Published by Elsevier Science B.V.