X-ray photoelectron spectroscopy is used to characterize two natural samples of laterite standard reference materials (certified geologically), a mechanical mixture of Fe2O3, SiO3, and Al2O3 in a 4:2:1 proportion. Fe2O3, SiO2, and Al2O3 samples were also analyzed for comparison purposes. Special attention was paid to peak shape, FWHM, comparison of the same XPS peaks of different samples, and peak shifts. The XPS results reveal the presence of some kind of iron aluminate prevailing on the surface of the laterite standard reference materials. It is also observed that the mechanical mixture exhibits a differential charging effect. Our report provides important information for the researchers doing XPS on these materials when they are used in catalytic reactions. (C) 2004 Elsevier B.V. All rights reserved.