Tools of combinatorial heterogeneous catalysis have been applied for the discovery of new leads of catalytic materials for the hydrocarbon (HC) selective reduction of NO under fuel lean conditions. In a period of 3 months, over 1500 different catalytic materials were explored that contained most of the single component and binary, and some of the ternary and quaternary combinations of metals from the periodic table over gamma-Al2O3, CeO2, 13X, Y, ZSM-5, Mordenite and beta zeolites. Diverse libraries were synthesized by the solution-based impregnation and ion-exchange methods for the oxide-based and for the zeolite-based supports, respectively. Catalyst screening was accomplished using array channel micro-reactors and mass spectrometry. A combination of Cu (10 wt.%) and Os (1%) ion exchanged 13X zeolitic material was determined to be an effective NO reduction catalyst lead with C3H6 in the temperature range of 250-600 degreesC. This catalyst also successfully passed a 36 h aging test at 450 degreesC in the presence of 12% steam and excess oxygen.