Tissue factor (TF) is the main physiological initiator of blood coagulation and may be important in the biology of a variety of solid malignancies, particularly where angiogenesis is a critical factor. TF is frequently encrypted in the plasma membrane of cells in contact with blood, and is exposed only after stimulation by certain agonists, Cancer cells variably express TF and cancer cell lines which exhibit multidrug resistance contain more TF than parental cells. TF is increased in both tumour-associated macrophages and blood monocytes and has been implicated in abnormal coagulation activation seen in patients with inflammatory conditions and cancer. TF is also found in urine (uTF) in a lipid-associated form, probably of kidney origin. uTF levels can be assayed in a cost-effective manner and may be clinically important, particularly in patients with renal disorders and malignancy. uTF levels are not significantly affected by age, gender or cigarette smoking. Copyright (C) 1999 John Wiley & Sons, Ltd.