In the summer of 1993, airborne and ground-based measurements of O3 and O3 precursors were made in the North Atlantic region. These studies were made by an international team of scientists collaborating as part of the North Atlantic Regional Experiment, an activity of the International Global Atmospheric Chemistry project of the International Geosphere-Biosphere Program. Previous measurements Fehsenfeld et al., this issue> have indicated that the amount of O3 produced from anthropogenic sources is greater than that reaching the lower troposphere in this region from the stratosphere and that ozone derived from anthropogenic pollution has a hemisphere wide effect at northern temperate latitudes. In this special issue the recently acquired data are used to better quantify the contribution of continental sources to the ozone levels over the North Atlantic. The aim of this overview is to provide the operational and logistical context of the study and to introduce the principal findings and conclusions that have been drawn from the results. ¿ American Geophysical Union 1996