Simultaneous chloroform (CHCl3) emission and ozone (O-3) deposition are regularly observed under nocturnal inversions during the summer months from and to the peat bogs in the vicinity of the Mace Head Atmospheric Research Station, Connemara, Co Galway, Ireland. Emissions were estimated using the nocturnal box model applied to routine atmospheric observations collected over a 14-year period from 1995 to 2008. Strict criteria were applied in the selection of events of low wind speed, under a stable night-time inversion layer in baseline air conditions, with no transport from Europe. The mean peatland CHCl3 flux was 2.91 mu g m(-2) h(-1) with highly variable fluxes ranging from 0.44 to 12.94 mu g m(-2) h(-1). These fluxes are generally larger than those reported previously for similar biomes and if representative would make a significant contribution to the global estimated source of CHCl3. Fluxes were not strongly correlated with either atmospheric temperature or the level of precipitation. Over the 14-year period there appears to have been a small increase in overall CHCl3 emissions, although we stress that the nocturnal box model has a number of limitations and assumptions which should be taken into account. (C) 2009 Elsevier Ltd. All rights reserved.