According to the data of continuous record during the vessel movement of water temperature and salinity of the surface layer on the Black Sea shelf of the Bosporus and in the strait for 1998—2000, their average three-year values were calculated: 15.45 °С; 17.37 ‰ and 15.20 °С; 17.48 ‰, and their latitudinal distribution and seasonal course were estimated. Specific latitudinal distribution of temperature and salinity of surface water layer have been noticed: isolines on the shelf are meridional because of climatic factor dominance; in the straight thermohaline characteristics differ essentially as a result of dynamic factor ¾ the process of mixing of water, which meet here. The Black Sea water coming to the straight begins its slower mixing with the Mediterranean Sea water in its near-bottom layer but after reaching the threshold the process from the slow one (velocity of temperature and salinity changes 0.5 °С and 1.1 ‰ per 1 degree of latitude accordingly) transforms into avalanche-like (with velocity 5.9 °С and 6.4 ‰ per 1 latitudinal degree), that determines the features of temperature and salinity distribution in the water of the Bosporus Straight. It has been found that the Black Sea water coming through the straight lowers its temperature per 1.5 °С and rises its salinity per 1.5 ‰. The seasonal course of water temperature in the channel is lower than on the shelf. Presence of two extremes (primary and secondary) were detected in a year course of water on the shelf as a result of mixing process in the Bosporus Straight the added water loses the secondary extreme of salinity. The year-round presence of low salinity waters is detected at the junction of the shelf and the channel (latitude 41.25 °N), which is explained by the influence of up to 10 km wide coastal current along the northern coast of Turkey. As a result, the water comes primarily from the coastal current, not from the open shelf waters.