The performance and durability of Cu-ZSM-5 were studied. Cu-ZSM-5 has fairly high NOx reduction activity but its durability is insufficient for practical use. We developed a new deNO(x) catalyst. In this catalyst, we call NOx storage reduction catalyst (NSR-catalyst), NOx emitted from an engine at lean A/F operation is stored and this stored NOx is reduced at stoichiometric or rich operation. This catalyst has been used on the Toyota CARINA with a lean-burn engine in Japan since 1994. This report outlines the results of our study on Cu-ZSM-5 and NSR-catalyst.