OBJECTIVE Topical corticosteroids are the current first-line therapy for vulvar lichen sclerosus (VLS). UV-A1 phototherapy may be a promising alternative treatment option, but controlled studies are lacking. OBJECTIVE To compare the efficacy of high-potent topical corticosteroids with UV-A1 phototherapy in the treatment of VLS. METHODS A 2-arm randomized clinical trial was conducted at a university hospital dermatology department according to the intention-to-treat principle with last observation carried forward. The study population comprised 30 female patients with VLS. METHODS Treatment of VLS with clobetasol propionate, 0.05%, ointment applied once daily for 3 months or medium-dose UV-A1 (50 J/cm²) home-based phototherapy, performed 4 times weekly for 3 months. METHODS Mean relative reduction of the total clinician's score (TCS) was considered the primary outcome measure. Secondary outcome measures included the reduction of pruritus and burning and/or pain according to a visual analog scale (VAS), a health-related quality of life score (Skindex-29), 20-MHz ultrasonography, and histopathological analysis before and after 3 months of therapy. RESULTS Fifteen patients were randomized in each treatment arm, and 2 patients dropped out in both treatment arms. After therapy, both therapies resulted in a significant decrease in mean TCS (51.4% [95% CI, 39.7% to 63.0%] for clobetasol ointment [P < .001] and 35.6% [95% CI, 18.2% to 53.1%] for UV-A1 phototherapy [P = .006]). No significant difference was found between both treatments (P > .05). The Skindex-29 (mean difference [MD], 29.6 [95% CI, 7.9 to 51.2] [P = .009]) and the VAS score for pruritus (MD, 4.6 [95% CI, 1.5 to 7.7] [P = .005]) and burning and/or pain (MD, 4.2 [95% CI, 1.9 to 6.6] [P = .001]) significantly decreased after clobetasol treatment. After UV-A1 phototherapy, the VAS score for burning and/or pain (MD, 3.2 [95% CI, 0.7 to 5.7] [P = .01]) was also significantly reduced; however, there was no significant reduction in pruritus (MD, 2.1 [95% CI, 0.5 to 3.7] [P = .16]) and in the Skindex-29 score (MD, 4.9 [95% CI, -12.6 to 22.4] [P > .99]). A significant reduction of the corium thickness and a significant increase in dermal density in 20-MHz ultrasonography as well as significant histopathological reduction of the inflammatory infiltrate was observed after clobetasol treatment but not after UV-A1 phototherapy. CONCLUSIONS Although resulting in a significant clinical improvement, UV-A1 phototherapy was inferior to the current gold standard treatment with topical high-potent corticosteroids with respect to practicability, relief of itch, and improvement in quality of life. UV-A1 phototherapy may be considered a potential second-line treatment for VLS. BACKGROUND clinicaltrials.gov Identifier: NCT01400022.