A series of samples have been prepared from high dispersion of CuCl2 into NaZSM-5 and HZSM-5 zeolites, and characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), hexane isotherms, and IR spectroscopy. The catalytic activity in selective reduction of NO shows that CuCl2/HZSM-5 catalyst exhibits higher conversion at 300 degrees C than that of CuZSM-5 prepared from an ion-exchange method. Correlation of catalytic data with infrared spectra for CuCl2/HZSM-5, CuCl2/NaZSM-5, and CuZSM-5 samples suggested that the catalytic sites can be assigned to synergetic effect of protons and copper species.