Historical hydrographic observations have been composited and objectively analyzed for the North Atantic Ocean for two pentads, 1955--59 and 1970--74, for the purpose of studying the temporal variability of the thermohaline structure of the deep North Atlantic Ocean. Statistically significant differences between the two pentads are found in the deep ocean. At 1750 m depth most of the North Atlantic increased in temperature (approximately 0.1¿C) and salinity (0.025%) from the earlier to the later period. An exception to this was a region in the eastern Atlantic between 33¿N and 50¿N where a cooling (0.1¿C) and freshening (0.025%) occurred. Changes at other depths as evidenced by difference fields of temperature along 24.5¿N and 36.5¿N are in agreement with differences found by Roemmich and Wunsch (1984) who described changes at these latitudes between sections taken in the late 1950's and sections taken in 1981. ¿ American Geophysical Union 1989