We measured the plasma levels of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in patients with disseminated intravascular coagulation (DIC) to examine the relationship between TFPI and vascular endothelial cell injury. Plasma TF (273 +/- 90 pg/ml) and TFPI (252 +/- 125 ng/ml) levels were significantly increased in patients with DIC compared with non-DIC patients. Plasma TF antigen level was significantly increased in pre-DIC patients (285 +/- 85 pg/ml), while the plasma TFPI level (152 +/- 54 ng/ml) was not markedly increased in such a state. The plasma TF/TFPI ratio was high in the pre-DIC patients (2.10 +/- 0.90), and low in the DIC patients (1.40 +/- 0.87) and healthy volunteers (0.84 +/- 0.26). There was no significant difference between the DIC patients with a good outcome and those with a poor outcome in terms of plasma TF levels, although the plasma TFPI level in the DIC patients with a good outcome (289 +/- 133 ng/ml) was significantly higher than that in those with a poor outcome (187 +/- 75 ng/ml). During the clinical course of DIC, plasma TF antigen was increased first, and an increase of the plasma TFPI level followed the increase in plasma TF level. These findings suggest that plasma TFPI is released from vascular endothelial cells and it may reflect vascular endothelial cell injury. It is conceivable that TF and TFPI may play an important role in the onset of DIC.