A wide variety of haloorganic compounds undergo reductive dehalogenation by certain anaerobic microorganisms. Metabolic reductive dehalogenation is coupled with energy-conserving respiratory electron transport in which a halogenated compound is used as the terminal electron acceptor, the biological process called dehalorespiration or halorespiration. Dehalorespiring bacteria may play important roles in the geochemical cycle with organohalogens in nature and have great promise in their application to the bioremediation of haloorganic contaminants derived from anthropogenic sources. During the past decade, a number of dehalorespiring microorganisms, including a unique group of strictly dehalorespiring bacteria, "Dehalococcoides", have been isolated and characterized at phylogenetic, physiologic, and genetic levels. Also, new perspectives of dehalorespiring bacteria have emerged based on information about genomics and molecular microbial ecology. This review article focuses on up-to-date knowledge of the biodiversity of dehalorespiring bacteria and reductively dehalogenating microbial consortia with special emphasis on those capable of transforming polychlorinated biphenyls and dioxins.