Ammonia decomposition proceeds at 300 degrees C over a catalyst consisting of ruthenium metal and CeO2 highly dispersed on Y-form zeolite. The catalyst, Ru-CeO2/YZ, is highly active for NH3 decomposition under conditions at which Y-form zeolite and CeO2 do not work. The decomposition rate is first order in ammonia. The initial rate of nitrogen adsorption supports the decomposition mechanism involving a rate-limiting step in dinitrogen desorption. Moreover, the load of ruthenium particles on CeO2/YZ catalyst makes an inhibition of the decomposition rate by hydrogen less strong. IR spectra for the catalyst indicate that the ammonia decomposition proceeds via the formation of the intermediate species, such as Ru-NH3, Ru-NH2, Ru-N-2 and Ru-H on the surface of ruthenium. The adsorption of hydrogen and XRD data support the idea that ruthenium is highly dispersed in the Ru-CeO2/YZ