Aerosol effects on atmospheric radiation are a leading source of uncertainty in predicting climate change. The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) was designed to reduce this uncertainty by measuring and analyzing aerosol properties and effects on the United States eastern seaboard, where one of the world's major plumes of urban/industrial haze moves from the continent over the Atlantic Ocean. The TARFOX intensive field campaign was conducted July 10--31, 1996. It included coordinated measurements from four satellites (GOES-8, NOAA-14, ERS-2, Landsat), four aircraft (ER-2, C-130, C-131A, and a modified Cessna), land sites, and ships. A variety of aerosol conditions was sampled, ranging from relatively clean, behind frontal passages, to moderately polluted, with aerosol optical depths exceeding 0.5 at midvisible wavelengths. Gradients of aerosol optical thickness were sampled to aid in separating aerosol effects from other radiative effects and to more tightly constrain closure tests, including those of satellite retrievals. Early results from TARFOX include demonstration of the unexpected importance of carbonaceous compounds and water condensed on aerosol in the United States East Coast haze plume, chemical apportionment of the aerosol optical depth, measurements of aerosol-induced changes in upwelling and downwelling shortwave radiative fluxes, and generally good agreement between measured flux changes and those calculated from measured aerosol properties. This overview presents the TARFOX objectives, rationale, overall experimental approach, and key initial findings as a guide to the more complete results reported in this special section and elsewhere. ¿ 1999 American Geophysical Union