Catalytic activity for soot combustion and efficiency of soot trapping of fibrous perovskite-oxide LaMnO3 and powder perovskite-oxide LaMnO3 were investigated. We have developed a new apparatus to produce a drizzly mixture of Soot/O-2/N-2 to imitate actual exhaust gas from diesel engines. By using this apparatus, it is possible to feed the mixture of soot, O-2 and N-2 continuously on catalysts at constant rates. It was found that the activities for soot combustion of powder and fibrous LaMnO3 were similar but that the efficiency for trapping soot by fibrous oxide was higher than that for trapping soot by powder oxide. Our method demonstrates a new possibility for the study of soot reduction under conditions close to those of an actual catalyst and filter placed after a diesel engine. (C) 2009 Elsevier B.V. All rights reserved.