Geological and limnological factors of Arctic and Antarctic deserts are disussed and compared. The lakes in the dry valleys range in size from under a kilometer in length and width to 6km long and 1.5km wide. Most of the larger lakes are in deep basins with depths ranging from 15 to over 70m deep. Ice cover is perennial and is in the order of 3.5m in late spring. All but one of the lakes a saline; dominant salts differ in various lakes. The hydrology and limnology of ice-free cold deserts in Antarctica differ considerably from those in the Arctic. Thermal gradients, salinity, and stratification within large Antarctic lakes are greater and ice cover is more persistent. Large, seasonal rivers prevalent in the Arctic are absent in Antarctica. The limnology of Lake Miers is discussed.