Histiocytosis X is an entity of neoplastic diseases of unknown etiology and pathogenesis. In the own case material, half of the patients presented with clinical symptoms originating in the head and neck areas (7/14). With respect to the clinical course, localized histiocytosis X should be distinguished from acute-disseminated and chronic-disseminated disease, the three corresponding with the classical eosinophilic granuloma, Hand-Schüller-Christian's and Abt-Letterer-Siwe's disease; transitional forms are well-known. Therapy is surgical in cases of localized eosinophilic granuloma and cytostatic in cases of disseminated disease; in the latter Vinca-alkaloids and corticosteroids are preferably used. Any kind of treatment, however, has to be individualized and modifications result from the thorough observation of the clinical course, which is unpredictable for the individual case. Planning an individual concept of therapy for each patient is most important and should be done by surgeons together with the pediatric oncologist.