Although relatively rare, pulmonary hypertension can be devastating for those individuals who are affected and has significant societal implications. The 2003 WHO classification separates PAH (idiopathic, specific disease linked) from pulmonary hypertension related to lung disease, thromboembolic disease, and pulmonary venous hypertension. Another form of pulmonary hypertension, persistent pulmonary hypertension (PPHN), occurs in the newborn. In general, PPHN is thought to be responsible for approximately 10% of admissions to neonatal intensive care units and can be a complicating factor in 5 of 1000 live births. Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are complex disorders that pose a significant threat to critically ill patients. They are usually related to direct lung injury or indirect injury from sepsis, trauma, and other disorders. Although these pulmonary disorders reflect distinct pathophysiologic mechanisms, current evidence strongly suggests that a common denominator underlying many of the established molecular and cellular elements is endothelial cell activation and dysfunction. This summary statement briefly summarizes the state of the science and suggests future avenues of public health research.