Various Ag-Pd/mordenite catalysts were prepared on washcoated honeycombs and tested in terms of NOx removal from diesel exhaust gas with (CH3)(2)O as a reducing agent at a practical high level of space velocity. The activity was dependent upon the palladium loading. In terms of NOx removal, the order of catalytic activity was Ag(3)/Pd(0.01)/mordenite > Ag(3)/Pd(0.1)/mordenite > Ag(3)/mordenite catalyst > Ag(3)/Pd(1.0)mordenite. It was found that a relatively small loading of palladium on Ag/mordenite catalysts led to a significant improvement in catalytic activity over a wide range of temperatures. The properties of these catalysts were also investigated by the NH3 temperature programed desorption (TPD) and BET method. It was found that Ag(3)/Pd(0.01)/mordenite had a larger amount of acid sites. It was concluded that Ag/mordenite catalyst with a small amount of palladium can effectively remove NOx over a wide range of temperatures using (CH3)(2)O as a reducing agent.