HEXOS is an international program for the study of evaporation and spray-droplet flux from sea to air. The program includes measurements in the field at moderate-to-high wind speeds, wind-tunnel studies, instrument development, boundary-layer modeling, and subsequent development of parameterization for use in synoptic and climatic models of the atmosphere and the ocean. Present accomplishments of the program are 1) a wind-tunnel study of the flow distortion around the Dutch research platform, Meetpost Noordwijk, 2) a pilot experiment at this platform in November 1984, and 3) an investigation of processes near the air-sea interface in a wind-wave simulation tunnel. The main field experiment, taking place in the autumn of 1986 at and around the Noordwijk platform, includes measurements of the fluxes of water vapor, spray droplets, sensible heat, and momentum, as well as the structure of the planetary boundary layer and the state of the sea. This multidisciplinary effort involves direct measurements from the platform, a mast, a ship, a tethered balloon, moorings, and an aircraft, plus measurements obtained remotely by laser scintillometer, lidar, and radar.