The present study has been carried out with the main objective of determining the prevalence rate of bacterial vaginosis (BV) in a population of asymptomatic pregnant women (8th to 9th month of pregnancy). Out of a total 1,441 patients examined BV was found to be present in 70 (4.9%). The diagnosis was made when an analysis of the vaginal discharge revealed the simultaneous presence of at least three out of four of the following laboratory indices: (1) direct Gram stain positive (bacterial flora mixed with Gram-negative coccobacilli and variable-gram predominant over the lactobacillus flora); (2) pH > 4.5; (3) positive odour test with KOH 10%; (4) presence of clue cells. After a discussion of the principal laboratory and clinical signs presently used for the diagnosis of BV, the authors suggest the exclusion of the evaluation of the appearance of the vaginal discharge from the standard diagnostic criteria. Further, three diagnostic methods are hypothesized for use in different settings.