A 25-year-old male patient with skin lesions of Langerhans' cell histiocytosis (LCH) was referred for periodontal treatment because of bilateral severely inflamed ulcerative periodontal lesions at the mandibular second premolar and first molar. On the left side, significant bone loss was revealed. Anti-infectious and surgical periodontal therapy resulted in significant probing pocket depth reduction and clinical attachment gains that were maintained for up to 24 months after surgery. Biopsies were taken during periodontal surgery. Immunohistochemical staining revealed that the periodontal lesions were uncommon periodontal manifestations of LCH. Reports of oral manifestation of LCH and treatment methods are reviewed. Keywords: eosinophilic granuloma, histiocytosis X, Langerhans' cell histiocytosis, periodontal disease, periodontal manifestation of systemic disease