[en] The Sediment Barrier Task Group (SBTG) coordinated laboratory studies of radionuclide migration through deep-sea sediments by investigators in six countries over a period of 12 years. The objectives of these studies were to evaluate the barrier properties of a variety of deep- sea sediments from study locations characterized by the Site Assessment Task Group (SATG), and to obtain site-specific data for use by the Radiological Assessment Task Group (RATG) in models of radionuclide transport through the sediments at the Great Meteor East (GME) and Southern Nares Abyssal Plain (SNAP) study locations in the North Atlantic Ocean. This volume presents a review of these laboratory investigations and the results obtained from them. Although the SBTG also participated in numerous geochemical investigations at the study locations characterized by the SATG, these field studies are not discussed here. For the convenience of the reader, however, this volume contains a brief description of the sediments from GME and SNAP, and the Mid-Plate Mid-Gyre I (MPG I) study location in the North Pacific Ocean. 130 refs., 48 figs., 11 tabs