Supporting Pt and Pd catalysts have been examined for the reduction of NO with H-2 in the presence of oxygen and moisture. Ail catalysts showed a conversion maximum in the NO reduction at around 373 K. An additional conversion maximum was found to appear at around 573 K over several metal oxides supporting Pd, and Pd/TiO2 gave the highest conversion at around 573 K among the catalysts tested. In the reaction at 373 K, NO might be reduced directly by H-2 both on Pt and Pd catalysts to give N-2 and N2O. At the conversion maximum of the Pd/TiO2 catalyst at 575 K, however, in situ generated NO2 seems to react with H-2.