Well-defined hexagon gamma-alumina ( gamma-Al2O3) nanosheets were successfully obtained with a sol-gel process under supercritical ethanol drying condition. The sol-gel of alumina precursors was carried out in refluxing aqueous solutions that contained excess urea and 0.1-0.4 M Al3+, always kept the [urea]/[Al3+] ratio constant at a value of 3.0. The obtained precursor precipitates were calcined at different temperatures in a muffle furnace in order to compare with supercritical ethanol drying. The effects of reactant original concentrations in the sol-gel solution, sol-gel precursor concentrations in the supercritical ethanol solution and time for removal supercritical ethanol vapour have been studied. Nano-gamma-alumina particles obtained by supercritical ethanol drying exhibited hexagon sheet characteristics with the diameter of 5-10 nm and always had the gamma-alumina phase. The formation mechanism of nanosheets gamma-alumina was also discussed. (C) 2008 Elsevier B.V. All rights reserved.