The results of hydrological survey of the largest lakes of the Yamal Peninsula – Neyto 1st, Neyto-Erto, Neyto-Malto, Yambuto and Yarato 2nd, undertaken in September 2007 are presented. The morphometric characteristics of these lakes as well as the hydrological properties of their water at the end of the autumn low water stage were determined. Many of the largest lakes of Yamal have a complex bottom topography due to the presence of cryptodepressions cutting deeply into the bottom. They are both shallow lakes with an average depth less than3 m and lakes with average depths exceeding 10–20 m. There is thorough vertical mixing of the water masses (even in deep-water hollows) due to the impact of wind and convection. Extremely low mineralization and very low content of hydrocarbonates in the water result from the dominance of atmospheric precipitation in the input part of the lake water balance. Greenish coloring of water in some of the surveyed lakes and moderate supersaturation with oxygen in all the lakes evidence a considerable development of cold-loving phytoplankton species (during the growing season it is promoted by a longer daylight duration).