Fe-ZSM-5 catalysts are prepared by FeCl3 sublimation between 320 and 850 degrees C. The catalysts are characterised by XRD, H-2-TPR, NH3-TPD, NO adsorption by DRIFTs, and catalytic activity is evaluated for N2O decomposition. The influence of high temperature (850 degrees C) and pretreatment environment (air, He, He+H2O and H-2) on the nature of iron species in Fe-ZSM-5 is further investigated by DRIFTs. High temperature FeCl3 sublimation results in decreased FeOx formation, easily reducible and narrow distribution of iron species in close proximity to alumina in Fe-ZSM-5. High temperature FeCl3 sublimation or pretreatment results in isolated hydroxylated iron species, -Fe(OH)(2), which are not significant in Fe-ZSM-5 prepared by 320 degrees C FeCl3 sublimation followed by calcination below 600 degrees C. Fe-ZSM-5 prepared by high temperature FeCl3 sublimation show high N2O decomposition activity and the improved performance can be correlated to -Fe(OH)(2) species in close proximity to alumina.