The catalytic behavior in the decomposition of N2O of (i) Rh supported over Al2O3 ZSM5, TiO2, ZrO2 and Mg-Al oxide, (ii) Ni- and Cu-containing mixed oxides obtained from hydrotalcite-type anionic clays, and(iii)Cu/zeolites (ZSM-5 and Beta) with different characteristics is reported and some of variables which influence the activity are discussed. In particular, the following aspects of the reactivity are shown : (i) the effect of prereduction of the samples, (ii) the reversible or irreversible deactivation by O-2, NO, H2O and SO2, and (iii) the role of the ion-exchange method used to prepare the Cu/ZSM-5. The interesting catalytic behavior of Rh/TiO2 and the comparison of its characteristics with those of Rh/ZSM-5 are also shown.