Lichen sclerosus of the vulva mainly occurs in older women, but shows another peak of incidence at the age just before puberty. The etiology of the disease, which is characterized by firm atrophy, is not known. There are some hints for a genetic disposition, such as a certain constellation of HLA and familial incidence. Our present case report is concerned with the clinical course of vulval lichen sclerosus in sisters, which had almost simultaneously developed. In both cases, the disease was successfully treated with a cream containing thyme extract; there were no side effects.