In August-September 1963, a high degree of stratification for both temperature and salinity was observed in the Laptev and East Siberian Seas. Temperatures decreased with depth and with distance away from the Siberian coast, and salinities decreased vertically from the bottom and toward the coast. The five large rivers emptying into the Laptev Sea influence the temperature-salinity characteristics to a great extent causing high temperatures and low salinities near the coast and in the upper layers seaward. The Lena River fluvial plume, on the basis of salinity distribution, was observed to extend in a north to northeasterly direction from the river delta. The combined effects of the Khatanga and Anabar River runoff extended in a northeasterly direction from the Khatanga River Estuary with vertical distribution of the low salinity water limited to the upper 10 meters. Water of three temperature-salinity relationships was observed in the East Siberian Sea in both 1963 and 1964. Near the coast, between the Indigirka River and Chaunskaya Bay, warm low salinity water was observed. In the sea's shallower western regions, cold water with slightly higher salinities was noted. Both of these water types can be attributed to river runoff with cooling and mixing in transit accounting for the colder water and higher salinities. Water in the eastern East Siberian Sea through Long Strait and into the Chukchi Sea was observed to have water as cold as -1.8C and as warm as 1.4C associated with salinities from 28 to 33%. Lower dissolved oxygen values were present in Lena River effluent than in water in the northern and western Laptev Sea. (Author).