Vast areas of the soil ecosystem are permanently frozen or are unfrozen for only a few weeks in summer. Permafrost soils are of global interest since a significant increase in temperature is predicted for polar regions. This volume summarizes recent knowledge on various aspects of permafrost and permafrost-affected soils, including typical properties of these soils, the distribution and biodiversity of permafrost microorganisms, examples for microbial activity in frozen soils and genomic and proteomic insights into cold adaptation of permafrost bacteria. The impact of global warming on microbial communities, carbon dynamics, geomorphology and frozen-ground engineering are further discussed. Other chapters describe the feasibility and limitations of methods for removing contaminants in frozen ground and consider terrestrial permafrost as a model for extraterrestrial habitats.