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.