The dataset comprises a wide range of physical and biogeochemical oceanographic and atmospheric parameters, plus additional biological measurements and observations. Hydrographic parameters include temperature, salinity, current velocities, fluorescence and attenuance, while biogeochemical and biological analyses of water samples provided measurements of dissolved gases, hydrocarbons, sulphur species, dissolved organic carbon (DOC), halocarbons, nutrients, pigments, bacteria, phytoplankton and zooplankton. Bird identification and cetacean abundance studies were also undertaken, as were tracer release experiments using both inert chemical (sulphur hexafluoride, SF6) and bacterial (Bacillus globigii) tracers. Meteorological data were also collected, including concentrations of various chemicals, supplemented by standard measurements of air temperature, pressure, irradiance, humidity and wind velocities. The data were collected in the North Atlantic Ocean and North Sea between 1996 and 1998, as follows: Eastern Atlantic off the coast of Ireland (June-July 1996 and May 1997); southern North Sea (October-November 1996); and North Eastern Atlantic between the UK and Iceland (June-July 1998). The data were collected during four cruises (RRS Challenger CH127, CH129, CH133 and RRS Discovery D234) using a variety of equipment, including instrumentation deployed at sampling stations (e.g. conductivity-temperature-depth (CTD) profilers) and underway sensors that ran throughout each cruise, yielding continuous measurements of both hydrographic and meteorological parameters. Discrete air and water samplers were also used to measure atmospheric and hydrographic parameters throughout each cruise. The data collection periods were associated with individual ACOSE air-sea exchange experiments: two Eastern Atlantic Experiments (EAE96 and EAE97); ASGAMAGE in the southern North Sea; and the North Atlantic Experiment, NAE. ACSOE was a 5-year UK NERC Thematic Research Programme investigating the chemistry of the lower atmosphere (0 - 12 km) over the oceans. The Marine Aerosol and Gas Exchange (MAGE) study group was the only component of the ACSOE Project that included measurements in the marine environment. ACSOE data management was a shared responsibility between the British Atmospheric Data Centre (BADC) and the British Oceanographic Data Centre (BODC). BODC handled the management of ship data as well as all other data collected in the water column during the ACSOE/MAGE cruises. BODC assisted in the onboard collection and subsequent working up of ship data, and assembled all marine data in BODC's relational database carrying out quality control and data processing as required. ACSOE was led by Prof. Stuart Penkett of the University of East Anglia and cruise principle scientists included representatives of the University of Newcastle Upon Tyne, and the University of East Anglia.