Anaerobic reductive dechlorination of chlorinated aromatic or aliphatic compounds is generally perceived as a rare and highly specialized activity in the environment. However, recent studies have revealed a phylogenetic cluster of marine and estuarine dehalorespiring bacteria within the green nonsulfur group that are capable of attacking a wide range of chlorinated pollutants and are widespread in the marine environment. Each microorganism described so far from this phylogenetic cluster appears to have reductive dechlorination activity. Furthermore, this group can dechlorinate a wide range of chlorinated compounds, including chlorinated biphenyls, benzenes, and ethenes, and multiple congeners within each type of organochloride. In this study we discuss the ability of polychlorinated biphenyl dechlorinators 0-17 and DF-1 to dechlorinate chloroethene and chlorobenzenes and we present the phylogenetic status of this group. Ongoing studies focus on the distribution and diversity of these microorganisms and their potential role in the global cycling of organochlorides in the marine environment.