Despite their widespread occurrence in soils, the ecology of Acidobacteria and their response to environmental perturbations due to human activities remain very poorly documented. This study was aimed at assessing changes in the diversity and abundance of Acidobacteria in soils contaminated with 2,4,6-trinitrotoluene (TNT) compared with nonpolluted soils. The analysis of Acidobacteria communities at two sites with long-term and short-term contamination revealed that TNT has a drastic impact on the relative abundance of Acidobacteria in soil bacterial 16S rRNA gene libraries. The disappearance of most Acidobacteria from these soils was concomitant with a shift in Acidobacteria community composition and a loss of diversity, although the extent of diversity erosion depended on the sampling site.