Critical illness due to severe sepsis and trauma are major causes of morbidity and mortality, and a substantial economic burden in the United States and worldwide. Despite advances in clinical care, patients with sepsis and trauma-associated respiratory failure represent specific populations with high rates of adverse outcomes. The etiology of respiratory failure in patients with severe sepsis and trauma is multifactorial, but acute lung injury (ALI) is one of the leading causes, and is associated with prolonged ICU and hospital stays, mortality, and long-term sequelae. Other than general supportive care, few specific interventions other than lung protective ventilation have been shown to improve outcomes in such patients. New approaches for understanding the pathogenesis and developing better therapies are urgently needed.