Up to present time, the majority of microorganisms could not be cultured by traditional methods because of the unsuitable conditions and media for biochemical and physiology requirement of bacteria, especially the anaerobic microorganism communities distribute in soil and sediment. Numerous molecular biological techniques based on the 16S rRNA gene have been widely used to analyze the microbial diversity such as DGGE (denatured gradient gel electrophoresis), t-RFLP (terminal restriction fragment length polymorphism), TGGE (temperature gradient gel electrophoresis). In this study, nested-PCR and DGGE had been used for the analysis of anaerobic reductive dehalogenation Dehalococcoides diversity within bacterial population from different detoxification biotreatments in field trial of heavy herbicide/dioxin contaminated soil of Da Nang and in situ detoxification of "active landfill" cells from Bien Hoa former military airbase. Bioremediated cell M5 in Da Nang and sample 1.2 in Bien Hoa showed a higher diversity of Dehalococcoides. On the other hand, the diversity of Dehalococcoides in 100DNT biotreatment at Da Nang after 10 years of treatment presented at much lower level. The lowest diversity of these bacteria was detected in lake sediments from Da Nang and sample 3.4 of bioremediated cells in Bien Hoa. Most sequences received from DGGE clones showed high identities of more than 98 percent in comparison with 16S rRNA gene of Dehalococcoides strains in GenBank. These clones were deposited in GenBank with accession numbers from IQ677605 to IQ677673. The results once again confirmed the existence of Dehalococcoides strains and also proved the role of Dehalococcoides in reductive dehalogenation of chlorinated aromatic compounds, which are components of herbicides/dioxip.