Fresh and dichlorophenol (DCP)-adapted sediments from two ponds near Athens GA exhibited distinctly different dechlorinating activities. These differences centered on the relative rates of reductive dechlorination in both fresh and adapted sediments and on the substrate specificity of the adapted sediments. Fresh Cherokee Trailer Park Pond sediment dechlorinated 2,3-, 2,4- and 2,6-DCP to monochlorophenols at a faster rate and after a shorter lag period than fresh Bolton's Pond sediment. Lag periods were not observed in either Cherokee or Bolton's sediments that had been adapted to dechlorinate either 2,3-, 2,4- or 2,6-DCP. Adapted Cherokee sediments exhibited faster dechlorinating rates and a broader substrate specificity than the adapted Bolton's sediments. The broad substrate specificity of each of the adapted Cherokee sediments contrasted sharply with the narrow specificity of the 2,6-DCP-adapted Bolton's sediment. The preference for reductive dechlorination was ortho>meta or para in sediments from both ponds. (Copyright (c) Springer-Verlag New York Inc. 1990.)