Fe-ZSM-5 catalysts were prepared by subliming FeCl3 into H-ZSM-5. The method used allowed Fe-ZSM-5 catalyst preparation by FeCl3 exchange at a desired sublimation temperature and was found to be more precise. The sublimation of FeCl3 into H-ZSM-5 was carried out at 320 and 700degreesC Fe-ZSM-5 prepared by sublimation of FeCl3 at 320 8 followed by rapid heating to 700degreesC and the catalyst prepared by subliming FeCl3 at 700degreesC were found to be more active for NO reduction with NH3 in the presence of simulated exhaust gases containing water vapor than catalysts prepared by subliming FeCl3 at 320 8 To determine the active sites, the catalysts were characterized by H-2-TPR, in situ DRIFTS of NO adsorption, NH3-TPD, XRD and chemical analysis methods. The observed NO conversion differences in selective catalytic reduction using NH3 could be correlated to the iron cation species present at different locations determined from diffuse reflectance infrared spectroscopy. Enhanced NO reduction activity was obtained when gamma positions in Fe-ZSM-5, corresponding to Fe2+ (NO) band at 1877 cm(-1) in DRIFTS, were preferentially occupied.