Background Bacterial vaginosis (BV) is the most common cause of vaginal discharge. The objective was to compare the prevalence of BV by Nugent score among African-American women who have sex with women (WSW) and women who have sex with women and men (WSWM) compared with an age-matched group of women who have sex with men (WSM). Secondary objectives were to correlate low versus high Nugent scores with vaginal symptoms among women with BV and to correlate BV diagnosis with sexual practices. Methods: A secondary analysis of clinical and laboratory data from African-American WSW (n≤73) and WSWM (n≤68) participating in the Women's Sexual Health Project (August 2011-October 2013) and a 3:1 age-matched group of African-American WSM participating in the Longitudinal Study of Vaginal Flora (August 1999-February 2002) at a sexually transmissible infection clinic (n≤423) was performed. Results:Compared with WSM, WSW and WSWM were significantly more likely to have BV based on the Nugent score (OR 2.63; 95% CI 1.55-4.48; P<0.01 and OR 3.67; 95% CI 2.17-6.21; P<0.01 respectively). WSW and WSWM with BV were not significantly more likely to have higher Nugent scores than WSM with BV. Among women with BV reporting symptoms, there was no significant difference in the proportion of women with low-positive versus high-positive Nugent scores. Women who participated in receptive vaginal sex (penile or digital) within the 30 days preceding study enrolment were significantly more likely to have BV (OR 2.50; 95% CI 1.57-3.63; P<0.01). Conclusions: WSW and WSWM were significantly more likely to have BV than WSM. Further analysis of sexual practices among sexual behaviour groups of women is needed to determine their potential impact on BV rates.