N2O decomposition over Fe/ZSM-5 made by the sublimation method was investigated. Further calcination or steaming treatment (700degreesC) increased the decomposition rate of N2O. FTIR showed that such treatments lead to the disappearance of Bronsted acid sites. The various catalysts have different apparent activation energies, confirming the presence of different active Fe species. The observation that after high-temperature calcination a higher activity is obtained while no dealumination occurs indicates a mechanism where neutral Fe oxide clusters occluded in the zeolite micropores react at high temperature with the zeolite protons to form [FeO](+)-like species.