Fe-ZSM-5 catalysts, prepared by different methods, have been characterized by TPR and XRD and tested in the NO-SCR by NH3. The sublimation method leads to the most active catalysts. Nevertheless the preparation starting from Fe(acac)(3), which is a preparation easy to implement from an industrial point of view, seems to be a very attractive alternative way. Oil the most active catalyst, Fe(0.83)(sub)ZSM-5, prepared starting from FeCl3, a study of the mechanism was undertaken. In the initial step of the SCR reaction, the oxidation of NO in NO2, the re-oxidation of Fell species in the active iron oxo species is the slow phase. (C) 2004 Elsevier B.V. All rights reserved.