The behaviour of Rh/gamma-AlO3-sepiolite monolithic systems in the N2O decomposition reaction using catalysts with rhodium contents between 0.2 and 0.8 wt.% were analysed. The observed increase of the catalytic activity with the metal loading was related to an enhancement in the number of active sites. The SEM-EDX results showed that rhodium was mainly located on the alumina particles. The variation of the reaction rate values with the inlet N2O and O-2 concentrations, suggested an apparent first order equation with respect to N2O and zero order for O-2. The presence of NH3 traces or water vapour in the feed decreased the catalytic activity, probably due to the competitive adsorption of NHx or OH species. The ammonia oxidation reaction took place, producing N2O as a secondary product. The monolithic catalysts developed operate with a low pressure drop achieving a N2O conversion higher than 90% at 773 K in the presence of oxygen, ammonia or water vapour in the stream. (C) 2004 Elsevier B.V. All rights reserved.