The catalytic properties of Pt, Rh and Co supported on mesoporous molecular sieves with MCM-41-type structure consisting of SiO2 and Al2O3 were studied for the reduction of NO with propene. Pt supported on siliceous MCM-41 was the most active catalyst, however, significant quantities of undesirable N2O were formed during the reaction. Pt supported on mesoporous Al2O3 and Rh supported on both mesoporous oxides showed a lower activity, but an improved selectivity towards N-2 formation. Co supported on MCM-41-type materials had only a low level of activity for the reduction of NO with propene. For Pt supported on MCM-41-type materials only a minor decrease in the activity was observed when water vapor was added into the reactant gas mixture, while on Rh- and Co- containing catalysts the activity strongly decreased.