Acute respiratory distress syndrome (ARDS) is a common entity in critical care medicine and associated with many diagnoses, including trauma and sepsis, which may lead to multiple organ failure and death. Pathophysiologically, increased capillary permeability is the hallmark of ARDS which is characterized by damage of the capillary endothelium and alveolar epithelium in association with impaired fluid removal from the alveolar space and the accumulation of protein-rich fluid inside the alveoli. The clinical management of patients with ARDS is even more difficult, because in the presence of capillary leakage in the lungs, adequate intravascular volume and cardiac preload are required to maintain organ perfusion. The amount of pulmonary edema fluid is, however, difficult to determine at the bedside. Pulmonary edema can be detected on physical examination and may be confirmed by chest radiography. However, it has been shown to be difficult to quantify the extent of pulmonary edema based on chest radiography or other non-invasive measures. The transpulmonary thermo-dye dilution technique has been introduced as an instrument to quantify the fluid in the pulmonary capillary bed, i.e., extravascular lung water (EVLW). This technique has shown to be potentially valuable in the management of critically ill patients and has been further developed to be clinically available nowadays as single transpulmonary thermodilution. The following review deals with the measurement of EVLW and its place in the management of critically ill patients with ARDS.