Background: Lichen sclerosus (LS) is a chronic inflammatory skin disease in which numerous therapies have been used, with only limited success. Because low-dose UVA1 phototherapy has been shown to be an effective treatment option for localized scleroderma, which shares several similar clinical and histologic features with LS, we initiated a clinical trial with this phototherapeutic modality in patients with LS. Methods: Ten patients suffering from extragenital LS were treated with low-dose UVA1 phototherapy 4 times weekly with single UVA1 doses of 20 J/cm². Forty treatment sessions were performed within 10 weeks, resulting in a cumulative UVA1 dose of 800 J/cm². Results: Low-dose UVA1 phototherapy resulted in a marked reduction of the clinical score and a significant (P < .05) decrease of ultrasonographically measured skin thickness as well as a highly significant (P < .001) increase of dermal density. The patients reported a remarkable softening and repigmentation of the affected skin. Conclusion: Analogous to the treatment results in localized scleroderma, low-dose UVA1 phototherapy seems to be an effective and well-tolerated treatment option for extragenital LS. (J Am Acad Dermatol 2002;46:251-5.)