Our objective was to determine the effect of body mass index (BMI) on response to bacterial vaginosis (BV) treatment. A secondary analysis was conducted of two multicenter trials of therapy for BV and Trichomonas vaginalis. Gravida were screened for BV between 8 and 22 weeks and randomized between 16 and 23 weeks to metronidazole or placebo. Of 1497 gravida with asymptomatic BV and preconceptional BMI, 738 were randomized to metronidazole; BMI was divided into categories: <25, 25 to 29.9, and ≥30. Rates of BV persistence at follow-up were compared using the Mantel-Haenszel chi square. Multiple logistic regression was used to evaluate the effect of BMI on BV persistence at follow-up, adjusting for potential confounders. No association was identified between BMI and BV rate at follow-up (p = 0.21). BMI was associated with maternal age, smoking, marital status, and black race. Compared with women with BMI of <25, adjusted odds ratio (OR) of BV at follow-up were BMI 25 to 29.9: OR, 0.66, 95% CI 0.43 to 1.02; BMI ≥30: OR, 0.83, 95% CI 0.54 to 1.26. We concluded that the persistence of BV after treatment was not related to BMI. Copyright © 2008 by Thieme Medical Publishers, Inc.