The Institut de Radioprotection et de Sureté Nucléaire (IRSN) performed a series of 85Kr air sampling campaigns at mesoscale distances (18-50km) from the AREVA NC La Hague nuclear reprocessing plant (North West France) between 2007 and 2009. The samples were collected in order to test and optimise a technique to measure low krypton-85 (85Kr) air concentrations and to investigate the performance of three atmospheric dispersion models (RIMPUFF, HYSPLIT, and ADMS),This paper presents the 85Kr air concentrations measured at three sampling locations which varied from 2 to 8000Bqm-3, along with the 85Kr air concentrations output by the dispersion models. The dispersion models made reasonable estimates of the mean concentrations of 85Kr field measurements during steady wind conditions. In contrast, the models failed to accurately predict peaks in 85Kr air concentration during periods of rapid and large changes in wind speed and/or wind direction. At distances where we made the comparisons (18-50km), in all cases, the models underestimated the air concentration activities. © 2013 Elsevier Ltd.