Fifteen years have passed since lung protective strategy to the patients with acute respiratory distress syndrome (ARDS) established. Recently, the new Berlin Definition of ARDS has been developed and this classified ARDS into three stages (mild, moderate, and severe ARDS), depending on the PaO2/FiO2. After this new definition of ARDS, each treatment to the patients with ARDS should be considered, depending on the severity of lung injury, such as prone position to the patients with severe ARDS, muscle paralysis to the patients with severe ARDS. In this review article, we review the history of lung protective strategy and ARDS definition, discuss the novel physiological approaches to minimizing ventilator-induced lung injury, and highlight a numbers of experimental/clinical studies to support these concepts.