Dioxin-pollution hotspots in Vietnam are former military air-bases and areas heavily sprayed with Agent Orange, a defoliant used during the Vietnam War. Agent Orange was a mixture 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4,5-tricholorophenoxyacetic acid (2,4,5-T) contaminated with dioxins. Spraying of the Agent Orange defoliant at the former Aso military airbase, its adjoining areas of Aluoi of Thua Thien Hue province and in Cua of Quang Tri province, Vietnam may have enriched for polychlorinated dibenzo-p-dioxin (PCDD) -dechlorinating bacteria in soils/sediments. Soil analysis revealed a high concentration of polychlorinated dibenzo-p-dioxins at these Agent Orange-sprayed areas, particularly at the former airbase, where 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) reached 900 pg/g. This study  examined (i) the capacity of the anaerobic bacterial community of soils/sediments from Agent Orange sprayed areas to reductively dechlorinate 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD), 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD) and 2,3,7,8-TeCDD; and (ii) phylogenetic analysis of enriched putative PCDD-dechlorinating bacterial community. Anaerobic microcosms were spiked with approximately 10 àM 1,2,3,4-TCDD or 2,3-DCDD for 19 soils/sediments collected from these sites. 1,2,3,4-TCDD dechlorinating activity was shown in all soils and sediments, with the exception of a sample collected from peatland at Camau, a supposedly non-polluted site. 2,3-DCDD dechlorinating activity occurred in 1 of 4 tested soils/sediments. High dechlorinating activity was shown at 4 sites, with almost all spiked 1,2,3,4-TCDD and 2,3-DCDD dechlorinated after four or six months of incubation at 27°C and accumulation of triCDD, diCDD, monoCDD and non-chlorinated dibenzo-p-dioxin daughter products. Two main echlorination pathways in the different soil/sediments were observed, with initial peri or lateral dechlorination. The enriched 2,3-DCDD dechlorinating community was also able to dechlorinate 2,3,7,8-TeCDD to 2,3,7-TrCDD after two-month incubation. A diverse Chloroflexi community was observed in the soil/sediment microcosms using Chloroflexi-specific 16S rRNA gene primers and DGGE analysis bacteria. A diverse Chloroflexi community and their increasing abundance were observed in the soil/sediment microcosms using Chloroflexi-specific 16S rRNA gene primers and DGGE analysis bacteria. The DGGE profile indicated enriched Chloroflexi putative PCDD-dechlorinating community quite different from well-known PCDD-dechlorinating Dehalococcoides ethenogenes strain 195 and strains enriched from sediment of Kymijoki river (Finland). The findings of this study indicate that PCDD dechlorinating bacterial community has become ubiquitous in PCDD polluted areas sprayed with Agent Orange. There is thus potential for using indigenous PCDD-dechlorinating bacterial community for detoxifying dioxin hotspots in Vietnam.