The catalytic activity of ion-exchanged saponites for NO reduction with hydrocarbons in the presence of oxygen was investigated. Silver ion-exchanged saponite (Ag-saponite) showed excellent catalytic activity for NO reduction with propene. The highest activity was obtained for Ag-saponite with a silver loading of 7-8 wt%, on which the addition of water vapor to the feed gas promoted NO reduction at temperatures below 400 degrees C. 2-Propanol and acetone served as more efficient reducing agents in the presence of water vapor.