Use of culture-independent studies have greatly increased our understanding of the microbiology of hypersaline lakes (the Dead Sea, Great Salt Lake) and saltern ponds in recent years. Exciting new information has become available on the microbial processes in Antarctic lakes and in deep-sea brines. These studies led to the recognition of many new lineages of microorganisms not yet available for study in culture, and their cultivation in the laboratory is now a major challenge. Studies of the metabolic potentials of different halophilic microorganisms, Archaea as well as Bacteria, shed light on the possibilities and the limitations of life at high salt concentrations, and also show their potential for applications in bioremediation.