Cu-ZSM-5 catalysts have generated substantial automotive interest. This work deals with interactions between nitrogen oxides and hydrocarbons on these materials from 25 to 225 degrees C using infrared spectroscopy. Go-adsorption of NO with propene on CuHZSM5 produced only marginal spectral differences compared to the state of preadsorbed propene on the catalyst, indicating minimal interactions between the adsorbates. Oxygen addition to NO plus propene on GuHZSM5 resulted in appreciable NO oxidation. Propene adsorption decreased considerably, apparently due to a strong affinity of NO2 for the hydrocarbon. The spectra also suggest additional carbonylation and carboxylation of adsorbed hydrocarbons due to NO2. In the presence of NO2 and hydrocarbons on CuHZSM5, a band appeared at 2590 cm(-1). This band did not emerge during similar adsorption on HZSM5. The co-adsorption experiments indicate the following order for extent of interactions between the oxidants and propene on CuHZSM5 : NO < O-2 < NO2.