Tissue factor is a transmembrane protein located on the surfaces of a number of cell types that binds coagulation factor VII/Vtra and serves as an essential cofactor for factor VIIa to activate efficiently its physiologic substrates, factor IX and factor X, eventually leading to thrombin generation. It is now widely accepted ttrat TF plays a key role in the initiation of blood coagulation during physiological hemostasis, whereas inappropriate expression of TF may be reqponsible for thrombotic disorders and for fibrin deposition occurring in a vari-ety of pathological conditions. Recently, TF has been also involved in processes other than coagulation such as intracellular signalling, metastasis and angiogenesis (l-3). During the last years quite a lot of evidence has accumulated not only on the biochemisfiry but also, mainly on the basis of in vitro studies, otr the cell and molecular biology of TF. The reader is referred to recent comprehensive reviews for these aqpects (1, L7). This brief review attempts to summarize present knowledge on the in vivo expression of TF and the role thereof in the health and especially in disease states. Emphasis will be given to those pathological conditions in which TF appears to play a prominent role.