Current meter records from 28 stations are used to define the flow of water near the bottom of central Long Island Sound. Records were made at two of the stations for over 1 year and for 10 days or more at most of the others. Tidal and nontidal flow components are separated. Random fluctuations of up to 10 day's duration occur in the nontidal flow; they are not directly influenced by wind, rainfall, river runoff, or variations in sea level aling the shore. Salinity observations show the presence of well-defined surface and bottom water layers. Mixing between these is confined to shore side zones where the water is less than 10 m deep and to shoals where strong turbulence is generated. The current meter data show the bottom water at depths greater than 20 m to be flowing upstream at a rate that decreases toward the head of the estuary. At depths less than 20 m there is a shoreward flow of bottom water toward the mixing zone. The salinity and current data are used to construct a circulation model for the sound. The large-scale flow is apparently due to gravitational convection associated with salinity differences. However, response to changes in the freshwater inflow is delayed by about 2 months because of the large volume of surface water relative to the freshwater supply.