The field determination of selenium species was obtained after stripping 1 l of water, removal of the water vapour by a water trap, and cryofocusing in a small packed chromatographic column hyphenated to a non dispersive atomic fluorescence detector. Water trap and purging conditions were carefully studied. Under routine operating conditions, absolute detection limits of 4 and 4.5 pg of Se for Me₂Se and Me₂Se₂ were obtained, respectively. Under routine conditions, linearity extended up to 1 ng as Se for the different species studied. The selectivity of the system is discussed in the presence of carbon-containing species. This system was applied to the determination of volatile selenium species in the Gironde estuarine environment (France). Me₂Se was found to be the main volatile selenium species in concentrations ranging from 0.8 to 6.3 pmol l^–1. Seasonal variations have been observed and commented upon. Correlation with water temperature and salinity is also discussed.