Ordered, organic monolayers were formed on gold slides by adsorption from ethanol of HS(CH2)10CH2OH, HS(CH2)10CH3, S(CH2)10CH2OH2, S(CH2)10Ch32, and of binary mixtures of these molecules in which one component was terminated by a hydrophobic methyl group and one by a hydrophilic alcohol group. The compositions of the monolayers were determined by X-ray photoelectron spectroscopy (XPS). Wettability was used as a probe of the chemical composition and structure of the surface of the monolayer. When monolayers were formed in solutions containing mixtures of a thiol and a disulfide, adsorption of the thiol was strongly preferred (approx. 75:1). Monolayer, Gold, Surface, Contact angles, Thiols, Disulfides. (mjm).