Removal of NO x from diesel exhaust gas using C 3 H 6 , CH 3 OH or (CH 3 ) 2 O as a reducing agent was investigated on Ag/Al 2 O 3 , Ag/ZSM-5 and Ag/mordenite catalysts over a wide range of temperatures. Among them, (CH 3 ) 2 O was found to be suitable for the elimination of NO x over Ag/mordenite catalyst at the relatively low temperature of 200°C to 350°C. CH 3 OH was suitable over Ag/Al 2 O 3 catalyst from 350°C to 450°C while the Ag/mordenite catalyst using (CH 3 ) 2 O was superior to the Ag/Al 2 O 3 catalyst using CH 3 OH with respect to the temperature range. The Ag/ZSM-5 catalyst had a poor elimination ability when compared with Ag/Al 2 O 3 and Ag/mordenite catalysts. The effects of Ag on mordenite and Al 2 O 3 were also investigated. It was found that Ag improved the removal of NO x in the higher range of temperatures with mordenite, while Ag improved the removal of NO x in the lower temperature range with Al 2 O 3 . It was concluded that Ag/mordenite catalyst using (CH 3 ) 2 O as a reducing agent has a good ability for NO x removal over a wide range of temperatures.