One hundred and seven patients with lichen sclerosus et atrophicus (LS&A) of the vulva were studied to determine the malignant potential of the LS&A. Five patients had coexisting invasive carcinoma of the vulva or perineum with the LS&A, and 1 patient had coexisting intraepithelial vulvar carcinoma on the clitoris. None of these, however, was known to have LS/A prior to the biopsy for carcinoma of the vulva. The high association of carcinoma and LS&A is probably a result of selection of 2 unusual lesions sent for consultation and evaluation. Squamous hyperplasia in the vulva occurred in association with LS&A in 37 (35%) patients, but only G patients had areas of dysplasia coexisting with LS&A. These areas of dysplasia, like the 5 invasive carcinomas, occurred in an area of the vulva where the LS&A was minimal or absent. Follow-up data were obtained on 92 patients with LS&A. Only 1 developed carcinoma of the vulva, which occurred 12 years after identification of the LS&A. When carcinoma arises in the vulva in a patient with vulvar LS&A, it tends to arise in areas of minimal LS&A or isolated areas of relatively normal vulvar skin. This study did not provide evidence of carcinoma arising from LS&A. Five of the 92 patients developed 6 malignant neoplasms in other sites, including carcinoma of the endometrium (3 patients), lung (1 patient), and simultaneous carcinomas of the colon and cervix