Isoprene fluxes from a Salix viminalis (willow) plantation in western Sweden were measured using the relaxed eddy accumulation (REA) technique. Fluxes of up to 0.23 mu g m(-2) s(-1) could be observed. A standard emission factor at 303 K and a PAR flux of 1000 mu mol m(-2) s(-1) was estimated to 0.98 mu g m(-2) s(-1) by using the G93 algorithm. The chemistry of an air parcel passing over a willow coppice plantation was investigated utilising a Lagrangian box model in which the measured isoprene fluxes were used as input data. Dispersion after the field was accounted for by a procedure based on the Gaussian plume model. The calculations indicate that, in most cases, the isoprene emissions have a small effect on the local air quality. (c) 2005 Elsevier Ltd. All rights reserved.