Abstract Given an accurate control of chemical composition, structure and thickness, monomolecular layers of fatty acids are used as model systems to study biological processes. Assembled as multimolecular layers on solid supports, these systems are used to prove the feasibility of secondary-ion mass spectrometry (SIMS) to investigate organic surfaces. A simple model can be applied to explain the observed sputtering phenomena. The yield of this process is, for the organic systems, approximately as large as that for inorganic systems, but the damaged cross-section is considerably larger. The latter determines the dependence of the intensities of various signals on the primary-ion dose. Yet it could be shown that the chemical composition of the organic system can be determined with a depth resolution of better than 25 Å.