The N2O-CO reaction has been studied on the Ir(110) surface in the temperature range from 300 up to 800 K and compared with the N2O-H-2 reaction on the same surface. At temperatures up to 550 K (depending on the N2O/reducing gas ratio), the reaction with H-2 is faster due to CO inhibition of the reduction of N2O by CO. Isothermal sustained oscillations in rate were found in the temperature range from 373 to 377 K, for very low CO/N2O ratios. The reaction products are N-2 and CO2. Interestingly, the reactant N2O oscillates in an almost counter-phase with the other reactant, CO. The period is around 60 s; also, highly correlated, synchronous events were found in regular time intervals. A model for the rate oscillations involves periodic transitions between a CO-rich (inactive) and a CO-poor (active) surface. In contrast, the rate oscillations for the N2O-H-2 reaction are related to periodic transitions between O-rich and O-poor surfaces.