It is now recognized that the hemostatic system plays an important role in cancer growth and dissemination, processes known to be vitally dependent on new tumor blood vessel formation (angiogenesis). There is also an increasing body of evidence supporting the link between the various components of the coagulation/fibrinolysis systems and angiogenic activity in cancer patients. Tissue factor (TF), thrombin, fibrinogen, fibrin, and plasminogen activation system, as well as platelets, all are able to promote angiogenesis. On the other hand, coagulation inhibitors, as well as cryptic (proteolytically released) domains of hemostatic proteins, are also known to act as angiogenesis inhibitors. Indeed, modulation (stimulation or inhibition) of angiogenesis may result from either classical functions of various molecular components of the hemostatic cascade, their less studied "alternative" activities, or both. Although much remains to be understood about this complex circuitry these considerations support the judicious use of anticoagulants in patients with malignancy as well as encourage the search for novel antiangiogenic activities that may reside within molecular and cellular components of the hemostatic system.