Cu-Zr-O catalyst is active and selective in the NO reduction by propene in an oxidizing atmosphere. This is due to the inertness of ZrO2 in hydrocarbon oxidation and its ability to disperse Cu. Other transition metal-zirconium mixed oxides were also tested for NO reduction by hydrocarbons in an oxidizing atmosphere. When propene is used as a reductant, Cu, Ni and Co supported on zirconia are active and selective catalysts. When propane is used as a reductant NO conversion decreases for all of the catalysts. The decrease is mild for Ni and Co but is very severe for Cu.