One major concern after surgery is postoperative pulmonary complications such as atelectasis, aspiration, pneumonia, and respiratory failure. Progress in preoperative and postoperative rehabilitation, in systemic management including respiratory management, and progress in understanding the pathophysiology of acute respiratory failure have improved prevention and the outcome of treatment. However, some conditions remain very difficult to treat, like respiratory failure accompanied by infection or multiple organ failure. In the 1960s, the concept of acute respiratory distress syndrome or adult respiratory distress syndrome was postulated. Tremendous amounts of basic and clinical research have been done to clarify the pathophysiology of and to establish treatment modalities for acute respiratory failure. Our understanding of acute respiratory failure has progressed from the role of microembolism syndrome to cellular components such as neutrophils and platelets and then to humoral factors such as endotoxins, complement factors, and numerous cytokines. In this article, the pathophysiology of acute lung injury and its diagnostic criteria, treatment modalities such as respirator management to protect lung tissue from barotrama and volutrauma by yielding hypercapnea (permissive hypercapnea), drug therapy with neutrophil elastase inhibitor, mechanical support using extracorporeal membrane oxygenation, liquid ventilation, continuous hemodiafiltration, and endotoxin elimination columns are discussed. Early diagnosis and early treatment are mandatory to improve survival in patients with acute respiratory failure, although we have not yet fully understood the pathophysiology of this disease entity sufficiently.