We report on a 78-year-old woman with a 47-year-history of lichen sclerosus et atrophicus of the vulva on which squamous cell carcinoma developed. The lesion started as a small nodule that increased gradually in size and became eroded. The tumour and the inguinal lymph nodes on both sides were excized. Physical examination, chest X-ray and sonography of the abdomen 15 months later showed no local recurrence or distant metastases. Lichen sclerosus et atrophicus of the vulva should be considered a possible precancerous condition.