In order to meet the stringent regulatory norms of NO, and CO emitted by automobiles, reduction of these pollutants has become an intense field of research. Various catalysts like Pt, Rh, Ir, Cu, and Fe have been found to possess high activity for the reduction of NO. However, the available detailed surface reaction mechanisms are not satisfactory in clarifying all the aspects of the simultaneous reduction of NO and oxidation of CO. Here we have developed a quantitative surface reaction mechanism based on elementary steps, in order to comprehend the phenomena of catalytic reduction of NO by CO. Eleven elementary steps are proposed for the NO-CO and NO-CO-O-2 systems on Pt group catalysts. The elementary reaction mechanism is coupled with the continuously stirred tank reactor/packed bed reactor models and the simulation results are validated against literature experiments for the NO-CO reaction on Pt, and the NO-CO-O-2 reaction on Ir catalyst. Despite the simplicity, the CSTR model is able to capture the observed phenomena well on Pt and Ir catalysts. The effect Of O-2 On the activity of CO for NO reduction is also analysed in detail through the simulations. (c) 2006 Elsevier B.V. All rights reserved.