Atmospheric research programs in global climate change and regional air quality are typically conducted as separate, albeit related, activities. The focus of global climate change research is to study, on a global basis, the regional distributions of radiatively-important gases and aerosols and to determine the their effect on the regional and global radiation balance. Regional air-quality research is focused on the atmospheric science that underlies regional and continental atmospheric chemical composition, with the goal of enhancing our ability to predict and monitor future changes, leading to improved scientific input to decision-making. In the past depending on the mission of the supporting agency or institution, research campaigns have focused on one or the other of these research areas. However, the distinction between the research objectives of these two areas of research is, at least in part, simply a matter of perspective and scale. Many of the chemical and meteorological processes of interest are common to both. Also, intercontinental transport is either the starting point or the end point of regional air quality concerns depending on whether you are on the western fringe (inflow) or eastern fringe (outflow) of a region. In recognition of this strong linkage, the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) combines the efforts of many separate institution and governmental agencies to conduct a joint regional air quality and climate change study in the summer of 2004. The combination of these programs provides the shared experience, the intellectual strength and critical mass of measurement technology and platforms to produce important new understanding at all scales on these complex atmospheric problems. In 2004, ICARTT will provide the coordination among these programs to allow a combine focus of unprecedented scope on three research areas of mutual interest with significant societal benefits. The three focus areas for this combined effort are regional air quality, intercontinental transport, and radiation balance.