Most of the sediment in process of deposition in Massachusetts Bay is derived by wave erosion from glacial drift or from bedrock on the coast and bottom of the Bay. Very little material is contributed from inland positions by streams or wind. The main agents of transportation are storm waves and currents and tidal currents. The sediments consist of silt, sand, and gravel. Bare bedrock occurs locally in belts at short distances from the shore. There is evidence of both emergence and submergence of the shoreline. Conditions at different places in the Bay and bottom samples in series from these same places are described in some detail and interpreted.