The interaction between NO and C2H4 was studied on ceria-supported Rh model catalysts (Rh/CeOX)). When the ceria is fully oxidized the primary reaction products observed in TPD are NO, N-2. CO, and H2O. This is similar to what is observed on Rh(lll) except that CO results from the reduction of the CeO2 by the C in the C2H4 On highly reduced ceria the only hydrogen-containing products are H-2 and a small amount of NH3. The O that comes from NO decomposition on Rh migrates to the CeOX before H2O formation occurs. N-2 and CO desorb from Rh/CeOX at a higher temperature than from Rh/CeO2. Soft X-ray photoemission indicates that the NO and C2H4 do not strongly interact to form new intermediates on Rh/CeO2. As the molecules decompose they produce N and C atoms on the surface, which eventually react to form N-2 or CO. The C and N do combine on reduced Rh/CeOX. CN is formed between 400 and 500 K. The CN produces more complex CXNY species at higher temperatures. These complexes decompose near 700 K to produce N-2 and CO. There are no desorption products that contain both C and N.