The authors sought to evaluate the pathogenetic and prognostic role of a procoagulant and hypofibrinolytic state in the adult respiratory distress syndrome (ARDS). Twenty-two consecutive patients admitted to the intensive care unit (ICU) for respiratory monitoring (n = 2) or mechanical ventilation (n = 20) were studied, of whom 13 had ARDS and 9 were at risk for the syndrome. Plasma levels of thrombin-antithrombin III complexes (TAT), the plasmin-alpha2-antiplasmin complexes (PAP), tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1) were measured within 48 h after admission, together with respiratory variables allowing computation of the lung injury score (LIS), and pulmonary microvascular permeability [67Gallium-transferrin pulmonary leak index (PLI)], as measures of pulmonary dysfunction. Blood was also sampled 6-hourly until 2 days after admission. The LIS and PLI were higher in ARDS than at risk patients, in the presence of similar systemic morbidity and mortality. TAT complexes were elevated in a minority of patients of both groups, whereas the PAP, tPA and PAI levels were elevated above normal in the majority of ARDS and at risk patients, but groups did not differ. Neither circulating coagulation nor fibrinolysis variables correlated to either LIS or PLI. Furthermore, the course of haemostatic variables did not relate to outcome. These data indicate that systemic activation of coagulation and impaired fibrinolysis do not play a major role in ARDS development and outcome in patients with acute lung injury.