In the last decade the incidence of thrombo-embolic diseases in which anti-platelet drugs may have been beneficial was estimated to be 2,500,000 patients affected by coronary artery diseases, 873,000 patients with cerebrovascular disease, i.e., stroke or transient ischemic attack, and 2,000,000 patients with peripheral arterial occlusive disease. The interaction between the platelet glycoprotein (GP) Ib-IX complex and von Willebrand factor (VWF) is known to initiate both hemostasis and pathological thrombosis, particularly in arteries and capillaries.