During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX), conducted off the East Coast of the United States in July 1996, the University of Washington research aircraft facility was used to obtain comprehensive in situ and remote sensing measurements of the physical and chemical nature of the aerosol and its effects on direct radiative forcing. This paper describes the airborne instrumentation used for this purpose, the sampling strategy, the times and locations of the 18 research flights, and a summary of the highlights of the results obtained to date. ¿ 1999 American Geophysical Union