Respiratory failure due to ALI and acute respiratory distress syndrome (ARDS) remains a major health problem despite significant progress in intensive care unit (ICU) care and ventilator management. It is also characterized by an unacceptably high mortality rate despite enormous expenditure of health care resources. Survivors of respiratory failure face long-term consequences concerning their quality of life. New therapies are needed to improve early survival and to decrease long-term sequelae of this syndrome. The purpose of this study is to identify biological markers of disease in patients with ALI that are predictive of either disease susceptibility or prognosis, or that identify novel targets of therapeutic intervention.