This review summarizes the current knowledge of the structure and function of von Willebrand factor and of the pathophysiologic features, diagnosis, classification, and treatment of von Willebrand's disease, the most common congenital bleeding disorder in humans. Specific regions of the von Willebrand factor subunit that are of functional importance have been identified. The structure of these functional domains of von Willebrand factor, as known to date, is described. A classification of von Willebrand's disease, based on the definition of structural and functional abnormalities of the molecule and initial characterization of genetic mutations, is discussed. With more precise characterization of molecular abnormalities, more selective therapeutic intervention for specific subtypes of von Willebrand's disease should eventuate.