In order to determine the prevalence of bacterial vaginosis (BV) among women attending a family health Center and to evaluate the accuracy of Amsel's diagnostic procedure relative to Nugent scoring for diagnosing this condition, we obtained vaginal specimens from 100 women under 50 years attending a FPC from April to November of 2006. Women were enrolled consecutively on a schedule basis and were not selected by symptoms of genital infection. VB was diagnosed in 32% women, without significant differences by age (p = 0,114). 87.5% women declared one sexual partner in the last 6 months. The Amsel's method had a sensitivity of 62.1%, and a specificity of 92.3%, with positive and negative predictive values of 81.8% and 83.3% respectively, being the presence of clue cells the most accurate parameter. Nevertheless, the lack of microscopes in the clinical practice limits the use of the Amsel's criteria. In conclusion, VB is a prevalent infection in the study population, being not associated with age or sexual activity. Diagnosis should be performed by the Nugent method.