Background: Bacterial vaginosis (BV) is a common disease in reproductive-age women and is associated to important gynecologic and obstetric complications. Aim: To study the occurrence of BV in apparently healthy women attending family planning clinics, using Amsel and Nugent diagnostic criteria. Material and methods: Two hundred thirty nine women consulting for symptoms associated to cervicovaginitis, were studied. A sample from the lateral walls of the vagina was obtained with a sterile swab for microscopic analysis, Gram stain and amine test. Results: According to Amsel and Nugent criteria a 31.1% and 31.8% BV prevalence was observed. The sensitivity and specificity of Nugent criteria, compared with Amsel criteria were 83.3% and 92.1%, respectively. Conclusions: The high prevalence of BV found in this study suggests that this vaginal infection should be diagnosed with standardized methods. Nugent criteria are economic easy to perform and sensitive and we propose that they should be used in local health centers. (Rev Méd Chile 2000; 128: 767-71).