A 69-year-old man was admitted to our hospital because of acute prostatitis. After admission he produced bloody sputum and chest radiograph showed bilateral infiltration of the upper lung fields. The fraction of neutrophils in the bronchoalveolar lavage fluid was 15.6%, lymphocytes were 33.6%, eosinophils were 26.6% and macrophages were 23.6%. No special findings were observed in the lung tissue obtained by transbronchial lung biopsy. After admission, he displayed acute respiratory distress syndrome with severe hypoxemia as dyspnea gradually progressed. We commenced treatment with high-dose pulse methylprednisolone and neutrophil elastase inhibitor under mechanical ventilation. Because severe hypoxemia was unresolved, HFOV was initiated on the 8th hospital day. His respiratory condition rapidly improved during HFOV. On the 17th hospital day, he was weaned from mechanical ventilation. HFOV seem to be safe and effective for patients with severe ARDS who failed conventional ventilation support.