Acute lung injury and acute respiratory distress syndrome are inflammatory conditions involving a broad spectrum of lung injury from mild respiratory abnormality to severe respiratory derangement. Regardless of cause (direct or indirect lung injury), pulmonary physiology and mechanics are altered, leading to hypoxemic respiratory failure. the use of positive pressure ventilation itself may cause lung injury (ventilator-induced lung injury, or VILI). VILI may amplify preexisting injury, delay lung recovery, and result in adverse outcomes. This article examines the evidence supporting lung-protective ventilation strategies and addresses the methods, outcomes, and potential obstacles to implementation of such approaches.