An 87-year-old woman was admitted because of high fever, progressive dyspnea and abnormal shadows on chest roentgenogram. Laboratory investigation on admission demonstrated a normal white cell count with neutrophilia (4000/microl, 90.5% neutrophils), an erythrocyte sedimentation rate of 10 mm/h and C-reactive protein value of 9.0mg/dl. Roentgenogram and computed tomographic scan of the chest shows bilateral infiltration and diffuse ground glass opacity, indicating acute respiratory distress syndrome (ARDS), but disseminated nodules, indicating miliary tuberculosis, were not found. Blood gas analysis demonstrated severe hypoxemia (PaO2 43.2Torr with 6L/ min oxygen). Based on the diagnosis of acute pneumonia and ARDS, intravenous administration of sivelestat sodium hydrate (100 mg/day), and continuous infusion of hydrocortisone (200 mg/day) were started. PaO2/FiO2 ratio improved but X-ray findings showed no improvement and a blood test revealed pancytopenia. Bone marrow biopsy revealed necrotizing epithelioid granuloma and acid-fast bacilli. A polymerase chain reaction (PCR) test detected Mycobacterium tuberculosis. Mycobacterium tuberculosis was also detected in sputum and urine. Therefore, we diagnosed miliary tuberculosis and transferred the patient to an infectious disease hospital. Miliary tuberculosis complicated with ARDS is relatively rare and the prognosis is extremely poor. Miliary tuberculosis should be kept in mind as a cause of ARDS.