The present study aimed to evaluate the prevalence of bacterial vaginosis, and the correlation of clinical Amsel criteria with Gram Nugent criteria for the diagnosis of bacterial vaginosis in a low risk population of pregnant women. Pregnant women under 28 weeks of gestation who were followed in the low risk clinics at two centers were evaluated for the presence of bacterial vaginosis using the Amsel clinical criteria, and underwent vaginal samples for Gram staining. Gram smears were examined for the diagnosis of bacterial vaginosis on the basis of Nugent's criteria. A total of 492 women were included in the study. Bacterial vaginosis was diagnosed in 1.6% (8/492) women on the basis of clinical criteria, and in 4.5% (22/492) according to Gram stain. The sensitivity and specificity of Amsel criteria compared with Gram stain were 35% and 99%, respectively. In accordance with other recent reports, the prevalence of bacterial vaginosis appears to be much lower in certain areas than figures previously suggested. In these populations, the correlation of composite clinical criteria defined in groups with high prevalence of bacterial vaginosis appears to be also poor.