The structural, textural, and chemical properties as well as the hydrophilicity of four different sol-gel aluminas were determined by different methods and compared with their activity in the catalytic epoxidation of cis-cyclooctene with aqueous H2O2. It was found that the hydrophilicity of the gamma-alumina surface is the principal factor responsible for the difference in catalytic activity. The hydrophilicity of gamma-alumina should be sufficient to guarantee a fast reaction with hydrogen peroxide on the surface but should not to be too high in order to allow the approach of olefin to the active sites. (C) 2004 Elsevier Inc. All rights reserved.