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The steady-state activity of NO reduction by C₃H₆, in lean conditions, was studied on a Pt(1%)/Ce_0.6Zr_0.4O₂ catalyst, in a plug-flow reactor, in the temperature range 100–500°C. The influence of reductive pre-treatments on the catalytic performance at low temperature (250°C) was investigated. Enhancement of the activity was found for the catalyst pre-treated in hydrogen at 350°C as compared to the sample pre-treated in H₂ at 800 and 1050°C. Moreover, transient reactivity tests of NO reduction by hydrogen were also carried out. As previously observed, the sample reduced at 350°C was the most active catalyst. In both types of reactions the temperature and the nature of pre-treatments had no effect on the selectivity to N₂ at the temperature of maximum NO conversion. Analyses by temperature programmed reduction (TPR), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD) and X-ray photoelectron …