Ni/alpha-Al(2)o(3) catalysts, prepared from nickel acetylacetonate, with low nickel contents (0.4-3 wt.%), have been characterized after a reduction treatment at 400 and 550 degrees C by infrared spectroscopy of adsorbed CO (IR-CO), X-ray photoelectron spectroscopy (XPS), hydrogen chemisorption measurements, and temperature-programmed reduction (TPR). Relatively high dispersion and particle size smaller than 8 nm were established. It was observed that an increase of the metal loading resulted in an enhancement of the average particle size and a decrease of the dispersion, indicating that suppression of hydrogen adsorption encountered in supported nickel catalysts with low metal contents is not necessarily due to the amount of nickel as reported in the literature, but instead, can be explained in terms of change of the particle size. (c) 2005 Elsevier B.V. All rights reserved.