[en] Background: Histiocytosis X is a rare granulomatous disease and it is still under debate as to whether this disease has to be counted among malignant tumors or benign immunologic lesions. The typical localization is confined to the bone. In rare cases histiocytosis X may be localized in the oropharyngeal mucosa. Patients and Methods: We report about a case of a 75-year-old woman presenting with histiocytosis X lesions solely located in the oral cavity. A total dose of 19.5 Gy was administered without any side effects. Results: Two weeks after completion of irradiation a rapid regression of mucosal ulcerations and improvement of symptoms occurred. In a follow-up of 24 months the patient is still in complete remission observed. Conclusion: Review of the literature revealed only casuistic reports about solitary lesions of histiocytosis X without bone involvement in the adulthood. External beam radiotherapy with total doses between 10 and 20 Gy seems to be effective for local control of this disease. (orig.)