The ice cores, representing accumulated past snowfall in the polar caps and ice sheets provides a basis for paleoclimate reconstruction. Paleo-climatic information derived from ice cores is obtained from four principal mechanisms: (1) analysis of stable isotopes of hydrogen and atmospheric oxygen which provide data on past temperatures; (2) analysis of other gases in the air bubbles in the ice which provide evidence of past trace gases, particularly CO2; (3) analysis of dissolved and particulate matter in the ice core that provide past data on dust accumulation; and (4) analysis of other physical properties such as thickness of the layers which provides evidence on past precipitation. Ice cores have been taken at multiple sites in Antarctica (age up to 800,000 years) and in Greenland (age up to 130,000 years). The mechanism by which stable isotopes of oxygen and hydrogen carry a temperature signal is described. Dating the layers in an ice core is a difficult matter, and a number of techniques have been employed. Counting annual layers visually is the most straightforward, but this method is limited to more recent times. Other, more sophisticated methods are described in the text. Ultimately, ice cores from Antarctica provide a wealth of data on past temperatures, carbon dioxide concentration, and levels of particulate matter.