Overly intense, persistent and dysregulated pulmonary and systemic inflammation has emerged as the leading hypothesis for the pathogenesis of ALI and its complications, but the contributory factors and mechanisms are incompletely defined. Several carefully-conducted prospective human studies have shown an association between specific inflammatory biomarkers in blood and BALF (both the initial levels at onset and changes over time) and important clinical outcomes in ALI. [Animal models have also demonstrated an association between inflammatory cytokines and non-pulmonary organ injury and dysfunction] In addition, one of the most important interventions (low-tidal volume ["lung protective"] ventilation) shown to decrease mortality in ALI is associated with reductions in inflammatory cytokines (IL-6, IL-8) in blood and bronchoalveolar lavage fluid [BALF].