Objective To determine the efficacy of fractional carbon dioxide laser (FXCO2) therapy for vulvar lichen sclerosus (VLS). Design Prospective, double-blind, sham-controlled, randomized trial. Setting Clinic specializing in vulvovaginal disorders. Population Forty women with active VLS confirmed with biopsy who abstaining from topical and/or systemic treatments for at least 4 weeks. Methods Women were randomized in a 1:1 ratio to receive either five sham laser treatments or five FXCO2 treatments in a 24-week period. Pre- and post-treatment biopsies were obtained on all participants. Study participants, treating clinicians, and evaluating pathologist were blinded. Main Outcome Measures Primary: pre- and post-treatment biopsy Histopathologic Scale (HS) findings. Secondary: Clinical Scoring System for Vulvar Lichen Sclerosus (CSS) Results There was a 0.12 reduction (improvement) in HS from baseline in the active treatment group (95%CI = -1.01, 0.78, p=0.79) and a 0.06 increase from baseline in the sham treatment group (95%CI - -0.81, 0.92, p=0.90). The change in HS between the active and sham arm was not statistically significant (-0.17; 95%CI = -1.14, 1.06, p=0.78). There was a 6.82-point reduction (improvement) in the patients’ CSS from baseline in the active (95% CI = -11.28, -2.37, p= 0.004) and a 4.83-point reduction in the sham treatment group (95% CI = -9.16, -0.51, p=0.03). In the clinicians’ CSS, there was a 0.82 increase (worsening) in the active (95% CI = -0.46, 2.11, p=0.20) and a 0.28 reduction in the sham treatment group (95% CI = -1.53, 0.97, p=0.65). Conclusions. FXCO2 is not an effective monotherapy treatment for VLS