There are contradictory reports about the synthesis and expression of TF antigen/activity in blood cells and plasma and in the surrounding environment of endothelial cells. In this review article we focus on the many divergent findings on the expression and presence of TF in various blood cells, plasma and endothelial cells in normal and pathological states. The widespread use of antibodies with inferior and misleading specificity and TF activity assays with low sensitivity/specificity, may be the major explanation for all the controversy. Based on our own experience and many other recent reports, pertaining to the concept of so called blood borne TF, we conclude that TF is exclusively expressed in and associated with circulating monocytes in blood of healthy individuals. However, several pathological conditions are associated with activated monocytes, shedding TF-rich microparticles that are transferred to activated platelets, neutrophils, and endothelial cells.