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. OXICOA (OXIdising Capacity of the Ocean Atmosphere) was a study of oxidant, radical and related gas-phase chemistry in the clean and moderately polluted marine atmosphere. The Eastern Atlantic Spring/Summer Experiments (EASE-96 and EASE-97) were carried to collect data. The dataset includes measurements of the OH and HO2 radicals, measurements of halogen oxide radicals at Mace Head in conjunction with a survey of potential organic halogen source gases. In EASE 96 the Cranfield Jetstream aircraft was deployed to measure the vertical and horizontal homogeneity of the air mass.