We have used a combination of density functional theory (OFT) and kinetic Monte Carlo (KMC) simulations to calculate the reaction rates for the selective oxidation of ammonia on RuO2(1 1 0) Our KMC simulations of 18 reactions among NHx(x-0-3) and OHx(x-0-2) species on RuO2(1 1 0) show 93% selectivity for NO in close agreement with experiment (similar to 95%) The chief factor in the high selectivity for NO on the RuO2(1 1 0) surface is the significantly reduced N diffusion (via N blocking) caused by various intermediates present on the RuO2(1 1 0) surface which severely inhibits the recombination rate of N + N -> N-2 but interfere far less with that of N + O -> NO owing to the nearby availability of O from dissociation of O-2 (C) 2010 Elsevier Inc All rights reserved