Alkylsiloxane layers that were prepared by reaction of alkyltrichlorosilanes, alkyltriethoxysilanes, and mono-, di- and trihydridoalkylsilanes with chromium oxide surfaces were assessed in terms of their hydrophobicity. Two general conditions were studied, in the vapor phase at elevated temperatures (70 degrees C) and in solution at 70 degrees C. The surfaces were characterized by contact angle analysis and X-ray photoelectron spectroscopy (XPS). The kinetics of the solution phase reactions of n-octadecylsilane and n-octadecyltrichlorosilane were also studied. Hydrophobic monolayers were achieved in all cases, but subtle differences in structure were found. (C) 2008 Elsevier Inc. All rights reserved.