The redox behavior of CuZSM-5 was investigated by flow microbalance and FTIR measurements using CO and NO as probe molecules. The weight change resulting from switching the flow of 10% O2 in He to pure He corresponded to the removal of extralattice oxygen and approximately 20% autoreduction of total copper ion by one electron. FTIR absorption spectra of CO over CuZSM-5 showed that the concentration of the Cu+ sites changed reversibly upon switching the pretreatment gas from He to O2. The combined experiments (flow microbalance and CO adsorption) proved that CuZSM-5 has a redox function at 500 °C. Continuous measurement of NO adsorption spectra using the same wafer, following a pretreatment in flowing He at 500 °C, also demonstrated the redox properties of CuZSM-5. During the early stage of NO adsorption, a sharp band at 2295 cm-1 appeared that could be assigned in several different ways. Changes occurring as NO underwent reaction on the surface were recorded.