Self assembled mixed component aromatic layers on gold, prepared from solutions of 4'-(4-mercaptophenyl)2,2': 6',2" terpyridine and mercaptobenzene, have been investigated by means of ToF-SIMS. For such a system, static SIMS provides quantitative information in excellent agreement with XPS data. The mixed layer is formed with a quasi-constant composition, almost independent of the ratio of the constituents in the starting solution. This indicates the existence of a particularly stable structure. The intensity behaviour of clusters ions in static SIMS spectra suggests that the surface layer is a homogeneous mixture rather than phase separated. Multivariate analysis of SIMS spectra allows to discriminate samples with very similar surface composition, but prepared from different starting solutions, providing a fine control of surface composition. (C) 2004 Elsevier B.V. All fights reserved.