We show the possibility of chemical tracing in solution down to a concentration of a fraction of an atto mol (10(-18)) by means of non-resonant surface enhanced Raman scattering (SERS). The experiments are demonstrated with rhodamine 6G dissolved in water. Based on our results here, we propose a technique for counting a small number of SERS active molecules in micro-droplets of liquid. It is argued that, by choosing the appropriate SERS enhancement condition, the technique could be used and implemented as a routine analytical method with unprecedented detection capabilities for the monitoring and tracing of important families of biomolecules. (C) 2003 Elsevier Science B.V. All rights reserved.