Manganese oxide catalysts supported on Al2O3 and Mg-Al2O3 composite were prepared from two different precursors, manganese acetate and manganese nitrate, with two manganese loadings. Catalytic performance was evaluated in ethanol combustion, which is a volatile organic compound used as solvent in print industries and a potential fuel for vehicles. The most active and selective catalysts to total oxidation were those prepared from manganese acetate. By means of a wide physicochernical characterization by X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), Raman spectroscopy, scanning electron microscopy (SEM), and specific surface area measurements, it was found that the best catalytic performance was obtained when manganese oxide species are highly dispersed on the catalyst surface. The formation of these surface species depends mainly on the manganese precursor and also on the support and the manganese loading. (c) 2007 Elsevier B.V. All rights reserved.