Electrospinning (ES) uses the injection of a polymer solution in an electrical field to produce non-woven nanowebs of polymer fibres with diameters of 50-500 nm. The use of functionalised polymers or additives allows the surface composition of the nanostructured material to be tuned as a function of the application. Determination of the molecular composition in the outer monolayer at the surface of such nanoscale objects is an analytical challenge. This paper reports on the possibilities and limitations in the use of S-SIMS for the qualitative and quantitative characterisation of molecular components in nanofibres prepared from polycaprolactone (PCL) with and without cetyltrimethylammonium bromide (CTAB). Specifically, attention is given to the quality of the mass spectra in terms of mass resolution and mass accuracy, the detection of surface enrichment and the possibilities of imaging. (c) 2006 Elsevier B.V. All rights reserved.