This presentation at the 2007 Aspen Lung Injury and Repair Conference provided a brief historical perspective from the 1998 Aspen Conference on Acute Lung Injury, highlighting the discussion of clinical definitions. There was also a review of the National Heart, Lung, and Blood Institute ARDS Network clinical trials, with an emphasis on the success of the lung-protective ventilation strategy in reducing mortality. In addition, there was a discussion of the recently completed fluid and catheter treatment trial, which demonstrated no benefit for pulmonary arterial catheterization over central venous catheterization for monitoring patients with acute lung injury (ALI). The trial demonstrated an increase in ventilator-free days with a fluid-conservative protocol. Finally, there was a discussion of recent experimental studies that show promise for cell-based therapy with mesenchymal stem cells for the treatment of endotoxin-induced ALI in mice. There were three objectives for this presentation at the 2007 Lung Injury, Repair, and Remodeling Conference: (1) to provide a brief historical perspective from the 1998 Aspen Conference on Acute Lung Injury; (2) to review major National Heart, Lung, and Blood Institute clinical trials conducted in the past 10 years by the ARDS Network; and (3) to review some of our promising work with cell-based therapy for experimental ALI.