Phenotypic and phylogenetic studies were performed on a hitherto undescribed micro-organism isolated from the human vagina. Comparative 16S rRNA gene sequencing studies demonstrated that the unknown strain constituted a new subline within the genus Atopobium. The unknown bacterium was readily distinguished from other Atopobium species by biochemical tests and electrophoretic analysis of whole-cell proteins. Based on phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as Atopobium vaginae sp. nov. The type strain of Atopobium vaginae is CCUG 38953T.