A catalyzed Diesel soot filter and process. The Diesel soot filter incorporates a porous filter element coated with a catalytic agent so that Diesel soot from Diesel exhaust gas is deposited into contact with the catalytic agent when Diesel exhaust gas is passed through the porous filter element and so that the ignition temperature or oxidation temperature of the deposited Diesel soot is reduced. The catalytic agent is a mixture of alkali metal and cerium oxides. The mole ratio of alkali metal to cerium of the catalytic agent is in the range of from 0.5 to 5.