In a population of 956 women, attending for contraceptive advice, 131 (13.7%) were found to have BV acording to Amsel’s criteria. Clue cells were detected in 200 (20.9%) women, a positive amine (’sniff’) test in 191 (20.0%), a vaginal pH≥4.7 in 243 (25.4%) and a ”characteristic” vaginal discharge in 104 (10.9%) women. Sensitivity, specificity, positive and negative predictive values in relation to BV were calculated for each of these four criteria. The detection of clue cells, an increased pH and a positive sniff test showed excellent sensitivity (86–100%) values, but had a less satisfactory positive predictive value (52–68%). Vaginal discharge was found to be a poor predictor of BV. The vaginal flora in women with clue cells, increased vaginal pH or a positive sniff test was very similar to that of the women with BV, every after excluding concomitant cases of BV and the three respective criteria. Thus, a positive amine test, which is easily performed, strongly suggests BV and a vaginal flora predominated by Gardnerella vagi- nalis, Mycoplasma hominis, Mobiluncus species and anaerobic species on one hand, and lack of lactobacilli on the other. When there is a clinical suspicion of BV, the sniff test is positive and differential diagnoses are excluded, one can safely treat a woman for bacterial vaginosis.