The purpose of the investigation was to study pulmonary extravascular water levels and pulmonary vascular permeability (PVP) in the pathogenesis of acute respiratory failure (ARF)/acute respiratory distress syndrome (ARDS). Twenty-nine patients with ARF/ARDS and 10 healthy volunteers were examined. Central hemodynamics and oxygen transport were explored, by using a Swan-Ganz catheter. Intrathoracic volemic parameters were studied by the transpulmonary thermodilution technique. PVP was assessed by the pulmonary 67Ga-labelled transferrin leakage index. Plasma colloid osmotic pressure (COP) was measured on an osmometer. In most patients with ARF/ARDS, the pulmonary extravascular water index (PEVWI) was found to be higher (mean 16.9 +/- 1.5 ml/kg). At the same time its value was not greater than 10 ml/kg in 7 (24%) of 29 patients. There were no correlations between PEVWI and PaO2/FiO2 and between pulmonary extravascular water and AaDO2. The PVP index (PVPI) measured by transpulmonary thermodilution was 3.2 +/- 0.2, it being normal in 13 (45%) out of 29 patients. The pulmonary 67Ga-transferrin leakage index was higher in all the patients than in healthy individuals (23.2 +/- 2.9 x 10(-3) vs 5.7 +/- 9.9 x 10(-3)) and correlated with PaO2/FiO2 (r = 0.71; p = 0.01). In patients with ARF/ARDS, COP was lower (19.9 +/- 0.7 mm Hg). There were correlations between COP and PEVWI (r = -0.34; p = 0.01), COP and PVPI (r = -0.40; p = 0.044), COP and PaO2/FiO2 (r = 0.35; p = 0.02). PEVWI correlated with the COP-pulmonary wedge pressure gradient (r = -0.45; p = 0.0024). Hypoxemia correlated with intrapulmonary shunt (Qs/Qt). There was no relationship between Qs/Qt and PEVWI in the group as a whole. According to the ratio of Qs/Qt to PEVWI, the patients were divided into 2 groups. Group 1 comprised 11 patients with the ratio < or = 2; Group 2 included 18 patients with the ratio > or = 2, i.e. with an unproportional shunt enlargement as to the severity of pulmonary edema. A correlation between Qs/Qt and PEVWI was found in both groups: r = 0.82; p = 0.001 with the ratio < or = 2 and r = 0.48; p = 0.04 with the ratio > or = 2. Diverse causes of shunt formation were histologically detected. Thus, pulmonary edema was not identified in 24% of patients with ARF/ARDS. Arterial hypoxemia is associated with the increase in the shunt, but, in a portion of patients, the shunt was caused with atelectasis unassociated with pulmonary edema. Increased pulmonary permeability for transferrin is detectable in ARF/ARDS irrespective the severity of pulmonary edema. The pathogenetic features of lung lesions should be taken into account while choosing a treatment for ARF/ARDS.