Bacterial vaginosis (BV), a clinical entity characterized by a change in vaginal ecology where the normal flora of lactobacillus morphotypes is replaced by a mixed microbial flora consisting of anaerobes and Gardneralla vaginalis, is considered to be the most common form of vaginal infection among women of reproductive age (1). Clinically, malodorous vaginal discharge, especially a fishy odour, is the most common symptom. Various studies have found the prevalence of BV to range from 15 to 30 per cent in non pregnant women and upto 50 per cent in pregnant women (2). Clinical studies have demonstrated an association of BV with adverse pregnancy outcomes, upper genital tract infections such as pelvic inflammatory disease, endometritis, post-gynaecologic surgery infections, cervicitis, urinary tract infections, cervical intraepithelial neoplasia, and increased risk of sexual acquisition of human immunodeficiency virus infection (3,4). given its high prevalence and association with obstetrical and gynaecological complications, detection of this entity in women is of paramount importance. Diagnosis of BV is confirmed clinically using the composite criteria described by Amsel et al (5). These include a thin homogenous discharge, elevated vaginal pH above 4.5, release of amines on addition of 10 per cent potassium hydroxide to vaginal fluid and the presence of clue cells, of which three need to be present for the diagnosis of bacterial vaginosis. However, Amsel’s criteria may not be adequate to diagnose patients, as approximately 50 per cent of BV patients may be asymptomatic (4). Further, there exists a continuum from normal lactobacillus-dominated flora through “to severe BV” with an intermediate catergory which the Amsel’s criteria fail to recognize. Thus, grading the microbial flora seen in Gram-stained vaginal smears, especially the scoring criteria proposed by Nugent et al (6), as an alternative method has become useful as a diagnostic tool. In this system, large Gram-positive rods (Lactobacillus morphotypes), small Gram-negative to gram-variable rods (Gardneralla vaginalis and Bacteroides morphotypes) and curved Gram-negative rods (Mobiluncus species) are quantitated and a summation score is obtained. This method has been shown to be sensitive for diagnosing BV, however, observers have often felt it to be complex and time consuming for routine practice and doubts have been raised regarding its interpretation by different observers (7).