Oceanographic observations were conducted aboard USS EDISTO (AGB-2) during DEEP FREEZE 63 and USS ATKA (AGB-3) during DEEP FREEZE 64. Emphasis was focused on the distribution of water masses in the Ross Sea and the identifying physical characteristics of each type. NAVOCEANO personnel obtained data at 122 stations during DF-63 and at 79 stations during DF-64. Included in these totals are 23 annual ice forecasting stations which were reoccupied both years along the Victoria Land coast and in McMurdo Sound to determine sea ice potential by the heat budget reversal. The stations occupied on DF-63 were in the western half of the Ross Sea and most of those occupied on DF-64 were in the eastern half. Station data include vertical distribution of observed temperatures, salinities, dissolved oxygens, and phosphate-phosphorus and machine computed densities, specific volume anomalies, dynamic height anomalies, and sound velocities. Selected cross-section profiles of observed physical and chemical properties are presented to illustrate the water masses in the Ross Sea. Water types are defined and discussed. From the data presented, it is evident that warmer water from oceanic depths moves in over the continental shelf and is forced to the surface causing the central Ross Sea to become ice free earlier than surrounding areas. Additionally, there is evidence of the formation of colder, more dense, Shelf Water during the austral winter which acts as a barrier to this warmer water intrusion into the south-southwestern extremities of the sea. (Author).