As a model for single layers of self-assembled monolayers, Langmuir monolayers of silver n-octadecanethiolates were prepared to study the interfacial properties involving the sulfur and metal ions. The interfacial property of the thiol groups was compared with those of two hydrophilic functional groups, namely, a hydroxyl and a carboxyl group. In situ real-time ellipsometry together with surface pressure-area isotherm measurements were carried out to gain insight into the structures of the monolayers and their silver complexes. Furthermore, Brewster angle microscopy was used to supplement the structural information obtaining real surface images with nanometer thickness resolution. The results are discussed in terms of the formation constant of silver complexes between silver and the functional groups.