ABSTRACT. For several decades Antarctic lakes have occupied a unique position among lakes of the world because of their extreme physical, chemical, and biological characteristics. Antarctica is the home of meromictic lakes. For a variety of reasons, most Antarctic lakes exhibit sharp chemoclines and unusual thermal profiles, and most are covered to some degree with perennial ice. The biological communities which exist in these lakes must be able to adapt to a suite of harsh environmental factors. Some of these include supersaturated levels of dissolved oxygen, extremely low light conditions on an annual basis, and thick ice covers which reduce or eliminate wind-induced internal water circulation. Perhaps one of the most unusual biological features of these lakes is the extensiveness of benthic microbial mats. These mat communities are representative of living stromatolites. The sediments which the stromatolites trap and bind provide an unusual geological record about episodic climatic events related to the wax and wane of the ice surface. Because of the intimate associations among the lakes and their surrounding terrestrial environments in terms of heat budgets, Antarctic lakes may also prove to be excellent laboratories in which to study the progress of predicted global warming.