Objetives. To determine the prevalence of bacterial vaginosis (BV) and associated factors among 18-29-year-old women in 20 Peruvian cities using PREVEN project data. Materials and Methods. In this cross-sectional study, BV was defined using previously provided vaginal discharge samples on slides, which were Gram stained and observed under a microscope to determine the Nugent scores. A BV diagnosis was applied to samples with scores of 7-10. Prevalence ratios (PR) and 95% confidence intervals (95% CI) were estimated using generalized linear models. Results. A total of 6,322 women participated in the epidemiological survey and provided vaginal swabs. The prevalence of BV was 23.7% (95% CI: 22.6-24.7) and was associated with a greater number of sexual partners in the last 12 months (PR: 1.22, 95% CI: 1.03-1.44, p=0.020 for two partners; PR: 1.46, 95% CI: 1.23-1.74, p<0.001 for three or more partners), not using a condom during last intercourse (PR: 1.16, 95% CI: 1.01-1.34, p=0.034), being a sierra resident (PR: 1.18, 95% CI: 1.05-1.31, p=0.004), and having abnormal vaginal discharge or a bad smell (PR: 1.20, 95% CI: 1.09-1.33, p<0.001). Conclusions. The high prevalence of BV highlights the need to strengthen health services aimed at the detection and treatment of this condition.