Two cases of Langerhans cell histiocytosis involving the vulva are reported. The clinical features of Case 1 have been previously reported. The patients, aged 31 (Case 1) and 52 (Case 2) years, had disease limited to the vulva at the time of diagnosis. In both cases, the vulvar lesions were composed of Langerhans cells with twisted nuclei and nuclear grooves, associated with eosinophils and other inflammatory cells. Immunohistochemical studies using fixed, paraffin-embedded tissue sections showed that the Langerhans cells were positive for CD1A and S-100 protein in both cases, supporting the morphologic diagnosis. The first patient had multiple local recurrences during 3 years despite radiation therapy and vulvectomy, but is currently in remission and being treated with thalidomide. The second patient experienced disseminated disease involving multiple bony sites and the mouth despite radiation therapy. Including the present two cases, 6 of 18 (33%) cases of isolated vulvar LCH subsequently disseminated, most commonly to bone; other patients had local recurrences. Thus isolated vulvar LCH has the potential for aggressive clinical behavior, either as local recurrence or disseminated disease. New treatment modalities are needed for this disease.