Microbial reductive dechlorination of [1,2-14C]trichloroethene to [14C]m-dichloroethene and [14C]vinyl chloride was observed at 4??C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-14C]m-dichloroethene and [1,2-14C]vinyl chloride to 14CO2 also was observed under these conditions. Copyright ?? 2005, American Society for Microbiology. All Rights Reserved.