Vulvar ulceration is a rare manifestation of histiocytosis X. A 13-year-old girl had a nonhealing vulvar ulcer for 1 year. She had been in remission from histiocytosis X and the ulcer was not recognised as a sign of disease recurrence until tissue biopsy was obtained for histopathological and immunohistochemical studies. This article stresses the importance of establishing an accurate diagnosis when chronic vulvar ulcers are encountered and reviews the literature on this uncommon presentation of histiocytosis X.