A library of about 1000 distinct catalytic materials were prepared and tested systematically for their NO reduction activities using array channel microreactors and mass spectrometry. Catalysts were prepared by individually impregnating 42 elements from the periodic table into five support materials of gamma-Al2O3, CeO2, SiO2, TiO2 and Y-ZrO2 at five different loadings. They were tested at 1 atm pressure, in the temperature range 100-500 C. and at a GHSV of 60,000 h(-1). The feed gas used was 500 ppmv NO, 500 ppmv C3H6, 1400 ppmv CO, 8% O-2, 10% H2O. and the balance helium. The most significant leads were Pt/TiO2 and Pt/SiO2, both of which exhibited superior performances, reducing the levels of NO by 25 and 20%, respectively. (C) 2004 Published by Elsevier B.V.