This paper presents an overview of the 1999 Atlanta Supersite Project coordinated through the Southern Oxidants Study and Georgia Institute of Technology (GIT) and funded by the U.S. Environmental Protection Agency (EPA) along with other sponsors who provided in-kind support primarily through existing studies. The Atlanta Supersite Project was located at the existing Southeastern Aerosol Research Characterization Study (SEARCH)/Aerosol Research Inhalation Epidemiology Study (ARIES) site on Jefferson Street in NW Atlanta, Georgia. The primary objective of the Atlanta Supersite Project was to evaluate and compare advanced measurement methods for particulate matter mass and its components. Methods included filter- and denuder-based time-integrated or discrete samplers, a variety of semicontinuous methods measuring mass, its major components (sulfate, nitrate, ammonium, organic carbon, elemental carbon, trace elements) and gas-phase precursors, and for the first time ever, a comparison among particle mass spectrometers; four in total. These data were complemented by meteorological data as well as gas-phase criteria pollutant measurements and other supplemental data such as particle physical properties, volatile organic compounds (VOC), oxygenated VOC, and NOy. The primary and supplemental data also were used to better understand the formation and accumulation of particulate matter in Atlanta and to better understand source-receptor relationships. This paper overviews the study, summarizing objectives, the site and measurements, and the relative reference data used for comparisons, and it overviews the meteorological and chemical characteristics of pollution in Atlanta during the study, puts the study in context of Atlanta and the southeast United States, and finally summarizes the key findings from the over 30 publications published, submitted, or in preparation. This paper also provides as complete a list as is currently available of those publications. Others certainly will be emerging over time. The comprehensive database is available through the Atlanta Supersite Project Web site sponsored by GIT (http://www-wlc.eas.gatech.edu/supersite/).