Objective: To evaluate whether the use of "breathable" panty liners (BPLs) alters the normal vaginal flora, increases the incidence of bacterial vaginosis and/or vaginal candidiasis, or causes vulvar irritation. Methods: A randomized controlled trial assessed the vaginal ecosystem of women without complaints of vaginal discharge. The study group (n = 53) wore BPLs for 10-12 hours each day for 75 consecutive days, whereas the control group (n = 54) wore only their usual underwear. At each of 6 visits during 3 menstrual cycles, participants underwent gynecologic examination with colposcopic evaluation and pH measurement, in addition to assessment of vaginal microbial flora, intensity of inflammatory processes, and presence of vaginal candidiasis/bacterial vaginosis in Gram-stained smears. Results: After 75 consecutive days of BPL use, 40/44 (90.9%) and 42/44 (95.5%) women reported no complaints of vaginal discharge or vulvar itching/burning, respectively. There was no significant difference between the study group and the control group with regard to positive vaginal fungus cultures (5/44 [11.4%] vs 8/50 [16.0%]; P=0.7848) or bacterial vaginosis (3/44 [6.8%] vs 2/50 [4.0%]; P=0.7974) at the end of the study period. Conclusion: After 75 days of BPL use, there was no significant increase in vulvovaginal candidiasis, bacterial vaginosis, vulvovaginal irritation, or vulvovaginal inflammation. (C) 2011 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.11516164