Rapid contaminant attenuation of chlorinated organics has been observed in vegetated sediments (i.e., wetlands). In these sediments, enhanced biological processes, primarily reductive dechlorination, can occur in the root zone that drives rapid natural recovery. Vegetating sediments in confined disposal facilities may provide an opportunity for mass removal during storage. Studies will be presented for plant-assisted bioremediation of hexachlorobenzene as a surrogate for dioxins and PCBs. Studies have focused on the understanding the mechanism of the vegetation effect. Two hypotheses are considered: first that reductive dechlorination is enhanced in vegetated sediments because the root surface serves as a location of enhanced activities of dehalorespiring and other degrading microbial populations and second, that by vegetating sediment contaminated with chlorinated organic compounds, belowground root matter will serve as source of H2, overcoming redox potential limitations in sediments. In addition to lab studies, application of these concepts to treat advecting groundwater at several field sites will be described.