The deep waters of the central and southern Greenland Sea are examined using Bartlett 1989 and 1990 summer data displayed at very high temperature and salinity resolutions. The mixing of Arctic Ocean Deep Water (AODW) with Greenland Sea Deep Water (GSDW) in proportions of about 1:1 to form ''new'' Norwegian Sea Deep Water (NSDW) is confirmed. However, the previously accepted route of this new NSDW through the ridge system into the Norwegian Sea, the Jan Mayen Channel, is shown to pass deep water only intermittently; a passage through Mohn's Ridge farther north, beginning near 72¿06'N, 2¿W, is identified as a more likely route. Part of the ultimate AODW-GSDW mixture is shown to continue on along the Greenland continental slope into the Iceland Sea. A peculiar isothermal condition was found in the deeper parts of the GSDW. This is postulated to result from upward diffusion of temperature from a layer initially having the adiabatic temperature gradient. Above the isothermal layer is one of warming and decreasing salinity, the result of recent successive deep convections to different depths.