A new catalyst for NOx storage/reduction was prepared to improve the activity of Ba-Pt/gamma-Al2O3 by replacing Ba with a mixture of Ba and Mg. The catalyst was prepared by impregnating I wt.% Pt and then the alkaline-earth metals (Mg, Ba) on commercial gamma-Al2O3. The tests have been carried out in a wide temperature range (ca. 200-400 degrees C) in order to understand the role of the mixture of alkaline-earth metals as a function of temperature. The behaviour of the two catalysts was different and indicated a synergetic effect between Mg and Ba. (c) 2006 Elsevier B.V. All rights reserved.