Background: We have undertaken a cross-sectional study that investigates the association between bacterial vaginosis (BV) and sexual practices in sexually experienced and inexperienced women. Methods: Participants were 17-21-year-old females who attend Melbourne University, Australia. Study kits that contained an information and consent form, questionnaire, swab, and slide were distributed. Information regarding demographic characteristics and a broad range of sexual practices were collected. Gram-stained, selfcollected vaginal smears were scored with the Nugent method. Associations between BV and behaviors were examined by univariate and multivariate analysis. Results: BV was diagnosed in 25 (4.7%) of 528 women (95% confidence interval [CI], 3.1%-6.9%). Importantly, BV was not detected in women (n=83) without a history of coital or noncoital sexual contact (0%; 95% CI, 0%-4.3%). BV was detected in 3 (3.8%) of 78 women (95% CI, 0.8%-10.8%) with noncoital sexual experience only and in 22 (6.0%) of 367 women (95% CI, 3.8%-8.9%) who reported penile-vaginal sex. BV was associated with a history of any genital contact with a sexual partner (P=.02). BV was strongly associated with 13 penilevaginal sex partners in the prior year (adjusted odds ratio, 7.1; 95% CI, 2.7-18.4) by multivariable analysis. Conclusions: This study shows a strong association between BV and penile-vaginal sex with multiple partners but found no BV in sexually inexperienced women, once a history of noncoital sexual practices was elicited. Our findings indicate that BV is not present in truly sexually inexperienced women.