Case-control study with 86 new HIV seroconverters (case patients) among 5110 women enrolled in a cervical cancer screening trial. Diagnosis of bacterial vaginosis (BV) was significantly associated with an increased risk of HIV seroconversion, after adjustment for demographic characteristics, other sexually transmitted infections, and sexual behaviors (adjusted OR, 2.01 [95% CI, 1.12–3.62]).  BV may account for a substantial fraction of new HIV infections in this setting. Treatment of BV and other interventions to promote normal vaginal flora warrant attention for HIV prevention. The Journal of Infectious Diseases 2005;192:1372-1380. Free access