In the last 50 years, there have been great research and developments in the definition and pathophysiology of acute respiratory distress syndrome (ARDS), the most progressive form of acute hypoxemic respiratory failure. Although there are various discussions and recommendations, the definition of ARDS is still based on the Berlin 2012 diagnostic criteria. Despite various studies in recent years, there is still no effective pharmacotherapeutic agent for the treatment of ARDS. Lung protective mechanical ventilation (low tidal volume, low plateau pressure, low driving pressure) in all ARDS patients, prone position, neuromuscular blockade (cisatracurium) in moderate-severe ARDS patients, and hydrocortisone therapy in sepsis-associated ARDS patients are treatments that contribute to survival. In this review, current changes in the definition and epidemiology of ARDS, recent pharmacotherapeutic research and mesenchymal stem cell therapies will be discussed in the light of newly introduced ARDS phenotypes.