Data from a randomized trial of oral periodic presumptive treatment (PPT) to reduce vaginal infections were analyzed to assess the effect of the intervention on a healthy vaginal environment (normal flora confirmed by Gram stain with no candidiasis or trichomoniasis). The incidence of a healthy vaginal environment was 608 cases per 100 person-years in the intervention arm and 454 cases per 100 person-years in the placebo arm (hazard ratio [HR], 1.36; 95% confidence interval [CI], 1.17-1.58). Sustained vaginal health (healthy vaginal environment for ≥3 consecutive visits) was also more frequent in the intervention arm (HR, 1.69; 95% CI, 1.23-2.33). PPT is effective at establishing and sustaining a healthy vaginal environment. © The Author 2011. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved.