A self-assembly process of N-[2-(4-imidazolyl)ethyl]11-mereaptoundecan-amide (Im-SH) on gold surface was monitored by in situ measurements of the resonant frequency and the resonant resistance of a quartz crystal analyzer (QCA) together with optical and atomic force microscopy. The Q factor was applied to evaluate the homogeneity of the adsorbed monolayer. A two-step process was involved in the monolayer formation. At the first stage, a fast adsorption to the surface up to 90 % was produced, and then the dot-like Im-SH monolayers became to reorganize and reassemble to form a much larger aggregated monolayer.