Temperature and salinity distribution and volume fluxes through the Strait of Istanbul were analyzed using the long-term monthly time series of temperature-salinity (1996-2010) and current profiles (1999-2010), collected from both ends of the strait. While the annual cycle of the upper layer temperature, with the minima in February and maxima in August, reflects the influence of air temperature with a near monthly phase shift, the annual cycle of the upper layer salinity, with the lowest values observed between April and September is mostly affected by the river discharge into the Western Black Sea. The seasonal variations of the lower layer temperature and salinity in the Strait of Istanbul are mostly influenced by flow blockages. Inversely proportional upper and lower layer volume fluxes indicate strong seasonal variations with the minimum and maximum values in April and October, respectively. The annual average upper and lower layer volume fluxes calculated from the high resolution dataset are 404 km(3)y(-1) and 250 km(3)y(-1) at the north end, and 430 km(3)y(-1) and 245 km(3)y(-1) at the south end of the strait, respectively.