The Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) was a 5-year Natural Environment Research Council (NERC) programme on tropospheric chemistry coordinated by the University of East Anglia and involving research groups from a number of UK universities and research institutes. The project had three consortia of UK institutes and universities, each of which focused on a different scientific topic. The aims of the Marine Aerosol and Gas Exchange (MAGE) Eastern Atlantic Experiment were to quantify input of Dimethyl sulphide (DMS) into a parcel of air, examine the oxidation of DMS and its reaction with nitrogen species with time, investigate the formation of new particles as a results of these transformations, and to discriminate between natural and anthropogenic fractions of sulphur and nitrogen using isotopic measurements. Data contains profiles of aerosol size and distribution and trace gases throughout the marine boundary layer, taken using the British Aerospace Jetstream aircraft.