An in situ EXAFS study has been done on a pre-reduced and pre-oxidised 1.16% Pt/gamma y-Al2O3 catalyst in order to determine the effect of 1% NO (balance N-2) versus temperature at atmospheric pressure on the platinum particles. Changes were observed in the crystallite morphologies from 200 degrees C due to sintering processes on the pre-reduced catalyst. On the pre-oxidised one, the phenomenon is much less pronounced. This study specifies the reactivity of platinum clusters deposited on gamma-alumina versus NO.