The ESPRIT collaborative research project (2007-2010) aims to contribute to the identification, evaluation and characterisation of 41 priority substances transported by stormwater, in two experimental sites in Lyon, France (one combined system and one separate system). At the outlet of both catchments, monitoring campaigns are carried out for a large number of storm events and for some dry weather periods. Most of the campaigns will deal with event mean concentrations, and a limited number of pollutographs will also be measured. In both sites, specific prototypes collect both dry atmospheric fallout and rain water, allowing estimating the dry and wet contributions of the atmosphere to the stormwater pollutant loads. In a first phase, screenings of the 41 substances will be performed. In a second phase, more accurate specific analyses for some substances will be carried out if necessary. A special effort will be devoted to evaluate the event variability of concentrations and loads. Models will be developed to extrapolate results to annual and multi-annual time scales and, if possible, to un-monitored catchments with similar characteristics.