Acute respiratory distress syndrome (ARDS) was first described about 30 years ago. Modern definitions and statements have recently been proposed to describe ARDS accurately, but none is perfect. Diffuse alveolar damage is the basic pathological pattern most commonly observed in ARDS, and the term includes permeability edema. The alveolar epithelium of the alveolar-capillary barrier is clearly a key component requiring repair, given its multipotent functional activity. Lung inflammation and neutrophil accumulation are essential markers of disease in ARDS, and a wide variety of pro- and anti-inflammatory cytokines have been described in the alveolar fluid and blood of patients. These molecules still have to prove their value as diagnostic or prognostic biomarkers of ARDS. Supportive therapy in ARDS improved in the past decade; mechanical ventilation with lung protective strategies and patient positioning are gaining interest, but the indications for corticosteroids for ARDS are still debated. Nitric oxide may have a place in the treatment of one-third of patients. Novel approaches, such as surfactant replacement and liquid ventilation, may further improve supportive therapy. Innovative interventions may be on the horizon in treatments that help to resolve or modulate common pathways of ARDS, such as inflammation (eg, granulocyte-colony stimulating factor) or epithelial repair (eg, keratinocyte growth factor).