Bacterial vaginosis is a change in flora, the cause of which is still unknown in the vast majority of instances. Bacterial vaginosis has generally been used to represent any change in vaginal flora resulting in an assumed loss of lactobacilli. However, whether such a flora represents the genetically normal state of some women is poorly defined. The present 'crude' diagnosis of bacterial vaginosis ought to be refined. The proposed impact of bacterial vaginosis on adverse pregnancy outcome is contradicted by therapeutic studies involving pregnant women that result in a change in flora to a lactobacillus-dominated vaginal flora, but have no influence on the course ofpregnancy. Most therapies recommended for bacterial vaginosis in non-pregnant women are often successful in the short term, but usually unsuccessful if the follow-up period after finishing therapy is prolonged. Although bacterial vaginosis is generally believed to be an endogenous condition, a number of behavioral factors are involved, such as the use of contraceptive and intimate hygiene products and smoking habits. Although bacterial vaginosis is not considered a true sexually transmitted infection, it is correlated to sexual activities. The current review elaborates on these matters and on the vaginal microbial ecology.