Removal of NOx from diesel exhaust gas using C3H6, CH3OH or (CH3)(2)O as a reducing agent was investigated on Ag/Al2O3, Ag/ZSM-5 and Ag/mordenite catalysts over a wide range of temperatures, Among them, (CH3)(2)O was found to be suitable for the elimination of NOx over Ag/mordenite catalyst at the relatively low temperature of 200 degrees C to 350 degrees C, CH3OH was suitable over Ag/Al2O3 catalyst from 350 degrees C to 450 degrees C while the Ag/mordenite catalyst using (CH3)(2)O was superior to the Ag/Al2O3 catalyst using CH3OH with respect to the temperature range. The Ag/ZSM-5 catalyst had a poor elimination ability when compared with Ag/Al2O3 and Ag/mordenite catalysts. The effects of Ag on mordenite and Al2O3 were also investigated, It was found that Ag improved the removal of NOx in the higher range of temperatures with mordenite, while Ag improved the removal of NOx in the lower temperature range with Al2O3. It was concluded that Ag/mordenite catalyst using (CH3)2O as a reducing agent has a good ability for NOx removal over a wide range of temperatures.