The authors report a case of Langerhans' cell histiocytosis (LCH) with temporal localization and rapidly evolving initial clinical presentation in a 12-year-old boy. This disease of currently unknown etiology is actually considered a proliferative entity of cells with phenotypic characteristics of normal Langerhans' cells. An immunoregulation defect leading to abnormal maturation and migration of Langerhans' cells might be the basis for LCH. According to the Hystiocyte Society diagnostic criteria, ATPase, S 100 and D-mannoxidase positivity in addition to typical hystopathologic findings are sufficient for diagnosis of LCH. Head and neck localization of LCH occurs in about 70% of cases; males are more frequently affected than females, age at presentation varies from a few months to 15 years. Presenting features, initial diagnostic evaluation, differential diagnosis and treatment protocol of a unifocal monosystemic temporal bone localization of LCH are presented.