Background. Bacterial vaginosis (BV) is the most common cause of vaginal discharge and is associated with important public health complications such as preterm birth and acquisition or transmission of human immunodeficiency virus and sexually transmitted infections. Continued controversy concerning the pathogenesis of BV has led to a lack of progress in prevention and management of this infection. Methods. Development of a conceptual model for the pathogenesis of BV based on review of past and current research. Results. Our model suggests that BV is initiated by the sexual transmission of Gardnerella vaginalis, which has the appropriate virulence factors to adhere to host epithelium, create a biofilm community, and successfully compete with lactobacilli for dominance in the vaginal environment. The genetic diversity of G. vaginalis may result in virulent and avirulent strains. Symbiotic relationships with normally dormant vaginal anaerobes lead to increases in the latter which contribute to the symptoms of BV. Conclusions. G. vaginalis is the pathogen responsible for the initiation of BV. Future research should focus on preventing its transmission and improved therapeutics for the biofilm infection that is caused by this pathogen and host anaerobes. © The Author 2014.