Solid-state ion exchange in the presence of air has been used to prepare Fe-MFI catalysts that exhibit activities comparable to preparations obtained under anaerobic conditions. Preliminary results obtained during the simultaneous catalytic reduction of NO and N2O with propane in the temperature range from 473 to 773 K show that Fe-MFI might be of interest for the treatment of exhaust gases containing NO, and nitrous oxide. Undesirable CO formed in a side-reaction can be oxidized to CO2 by promotion of Fe-MFI with small amounts of Pt.