A number of adhesion molecules on neutrophils and the pulmonary capillary endothelium mediate the neutrophil accumulation in the lungs at the onset of adult respiratory distress syndrome or acute lung injury (ALI). P-selectin, located on both vascular endothelial cells and platelets, has been shown to be one of these neutrophil-endothelial cell adhesion molecules. In this study, we measured the soluble form of P-selectin in plasma (PPS) from 19 patients (surviving, 11; deceased, 8) with ALI due to various causes and assessed the clinical significance of this measurement. Twelve healthy subjects and 29 patients with other pulmonary diseases, including idiopathic pulmonary fibrosis (IPF) (n = 8), sarcoidosis (n = 5), pneumonia (n = 8), and sepsis without ALI (n = 8) were also studied for comparison. PPS in patients with ALI (474.5 +/- 366.8 ng/ml, mean +/- SD) were significantly higher than those in control subjects (98.8 +/- 39.7, p < 0.01) and in patients with IPF (210.4 +/- 76.6, p < 0.05), sarcoidosis (135.2 +/- 71.5, p < 0.05), pneumonia (225.3 +/- 81.0, p < 0.05), and sepsis without ALI (271.8 +/- 46.5, p < 0.05). There was no significant difference in PPS levels between seven patients with and 12 patients without multiple organ failure. Lung injury scores correlated significantly with the PPS level (r = 0.605, p < 0.05). PPS levels of deceased patients with ALI (841.0 +/- 252.4) were significantly higher than those of surviving patients with ALI (208.0 +/- 109.2, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)