The chemical deposition of PbS on self-assembled monolayers of 16-mercaptohexadecanoic acid formed on evaporated gold was investigated. In situ evaluation of the thickness of the crystalline film and of the kinetics of crystal growth was carried out by surface plasmon spectroscopy (SPS). The SPS measurements were correlated with structural and morphological data on the PbS films, as obtained by transmission electron microscopy and scanning electron microscopy, thus enabling the film structure at precise thicknesses to be identified. The applicability of SPS measurements to such a system was demonstrated. The microscopical analysis clearly showed that the film exhibited a marked structural change at a thickness of 25 nm. It was proposed that the film formed by an ion-by-ion mechanism.