Langerhans' cell histiocytosis (LCH) is a disorder of unknown etiology, characterized by abnormal proliferation of cells of the dendritic cell lineage. The acute disseminated form of the disease characteristically occurs in children younger than 3 years of age. More indolent forms of LCH occur primarily in older children and young adults. The prognosis for patients with LCH is good. We report a 28-year-old man with acute disseminated LCH who initially presented with fever, chills, and dry cough. Diagnosis of LCH was confirmed by bronchoalveolar lavage fluid cytology, and skin and bone marrow biopsies. Conventional chemotherapy was not given, because of the patient's poor clinical condition, including respiratory failure, unstable vital signs, and impaired consciousness. Salvage thalidomide therapy was started on the 12th day of hospitalization. The patient died from multisystem LCH with septic shock and multiple organ failure on the 22nd day of hospitalization. This report illustrates the diagnostic features and treatment of LCH in a rapidly fatal case of adult LCH.