Polychlorinated dibenzo-p-dioxins (PCDDs) are a class of toxic organic compounds released by a number of industrial processes. Sediments of the Passaic River in New Jersey are contaminated by these compounds. To explore the ability of native organohalide respiring bacteria to dechlorinate PCDDs, we first enriched bacteria from sediments of the Passaic River on two organohalides, trichloroethene (TCE) and 1,2-dichlorobenzene (DCB). We then used these enriched sediment cultures and original, unamended sediment as the inocula in a secondary experiment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD), 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD), and 2,7-dichlorodibenzo-p-dioxin (2,7-DiCDD) as target organohalides. We observed dechlorination of 1,2,3,4-TeCDD by all inocula, although to different extents. We observed progressive dechlorination of 2,3,7,8-TeCDD only in bottles inoculated with the DCB enrichment culture, and dechlorination of 2,7-DiCDD almost exclusively in bottles inoculated with the original, unamended river sediment. Dechlorination of 1,2,3,4-TeCDD was more rapid than that of the other amended congeners. Phylotypes within the class Dehalococcoidia associated with organohalide dechlorination were differentially enriched in DCB versus TCE enrichment cultures, indicating that they may play a role in dechlorination of the PCDDs.