FEMS Microbiology Ecology is proud to present this latest thematic issue on Anaerobic Biological Dehalogenation. Knowledge on anaerobic microbial dehalogenation has advanced significantly since its first discovery. Understanding of the biochemistry, physiology and ecology of organohalide-respiring bacteria (OHRB) has allowed development of bioremediation technologies for clean-up of contaminated sites. At the same time, a fundamental understanding of the processes, enzymes and organisms involved has allowed to discover new exciting features in biochemistry and microbiology. OHRB are either members of novel bacterial genera or already known ones with other metabolic features indicating the importance of horizontal gene transfer in this anaerobic respiration process. Reductive dehalogenases, thus far discovered, are all corrinoid-containing enzymes revealing unexpected biochemical features of this cofactor normally known to be involved in alkyl-transfer reactions. This special thematic issue shows nicely that there remains still a lot to be discovered regarding anaerobic biological dehalogenation.