Closely spaced salinity and temperature measurements in the region of the East Greenland Polar Front from 75 ¿N to 79 ¿N in October-November 1981 are presented. The Return Atlantic Current (RAC), having a core of relatively warm and saline Atlantic Intermediate Water (AIW) (T=0.5¿ to 3.0 ¿C, S=34.9 to 35.0), was found everywhere along a steep front separating it from the colder, fresher Polar Water. A narrow front jet was found to have velocities greater than 0.80 m/s where the station density was great enough to resolve its concentrated character. Notable fine structure was present, especially in the warm AIW just east of the front. A cold, saline water, forming a knee in the temperature-salinity correlation, was present in the upper margins of the RAC. The knee is formed primarily by warm AIW or Atlantic water flowing under the upper layers of water flowing from the Arctic Ocean. Calculations are presented to show that an initially isothermal underflow could be modified to a thick thermocline by double diffusion. Calculations of the rate of cooling of fine-structure elements by double diffusion indicate that the fine structure would have a limited lifetime (about 12 days) if its waters were not continually replenished.