The NASA Upper Atmosphere Research Program has funded a multi-year, multi-mission project, the Stratosphere-Troposphere Exchange (STE) Project, whose goal is to improve our understanding of the processes by which trace constituents are exchanged between the stratosphere and troposphere. The project is managed by the Atmospheric Experiments Branch, NASA Ames Research Center. Project scientist is E.F. Danielsen, and project manager is P.B. Russell, both of Ames Research Center. Scientific guidance is provided by an executive committee chaired by J.R. Holton, University of Washington. Project plans call for five major missions using the NASA U-2 and ER-2 high altitude aircraft in the extratropics, the subtropics, and the equatorial region in the years 1984–1987.