For the past two years, oceanographers in North America and Europe have been preparing a new study of a familiar oceanographic process: the spring phytoplankton bloom. Study of the bloom will be coordinated through the Joint Global Ocean Flux Study (JGOFS), whose principal objective is to understand on a global scale the processes controlling the fluxes of carbon and other biogenic elements in the ocean. In 1989, JGOFS begins a six-nation, eight month investigation of biogeochemical processes in the North Atlantic Ocean. This experiment will emphasize observation of the spring phytoplankton bloom and its biogeochemical consequences along longitude 20°W, between 15° and 60°N latitude, from March to October. The North Atlantic Bloom Experiment is intended to be a pilot study for future JGOFS experiments, but its origins go back exactly a century, to the studies of the German oceanographer Victor Hensen.