The adhesive protein von Willebrand factor (VWF) contributes to platelet function by mediating the initiation and progression of thrombus formation at sites of vascular injury. In recent years there has been considerable progress in explaining the biological properties of VWF, including the structural and functional characteristics of specific domains. The mechanism of interaction between the VWF A1 domain and glycoprotein Ibalpha has been elucidated in detail, bringing us closer to understanding how this adhesive bond can oppose the fluid dynamic effects of rapidly flowing blood contributing to platelet adhesion and activation. Moreover, novel findings have been obtained on the link between regulation of VWF multimer size and microvascular thrombosis. This progress in basic research has provided critical information to define with greater precision the role of VWF in vascular biology and pathology, including its possible involvement in the onset of atherosclerosis and its acute thrombotic complications.