Subduction zones are the most dynamic tectonic environments on the face of Earth. Most subduction zones are submarine and at many, large accretionary prisms are formed of sediments scraped from the subducting oceanic lithosphere. These prisms grow in a water‐saturated environment; consequently, their tectonic, thermal and chemical evolution is strongly influenced by fluids, and the role of the aqueous phase must be considered in any study in this realm.In view of widespread and growing interest, the North Atlantic Treaty Organization and National Science Foundation sponsored the workshop “The Role of Fluids in Sediment Accretion, Deformation, Diagenesis and Metamorphism at Subduction Zones,” which convened September 19–23, 1988, at Il Ciocco, Tuscany, Italy. This meeting assembled 60 geologists, geochemists and geophysicists representing eight countries whose interests spanned both marine and continental environments.