Based on previous epidemiologic studies it is estimated that in the Netherlands the referral based prevalence of moderate to severe von Willebrand disease (VWD) is approximately 1 in 10,000 (1650 patients). This does not include patients with mild type 1 disease (VWF levels 30-50 U/dL), or individuals with borderline VWF levels with a mild bleeding phenotype, of which the prevalence is higher and may even reach 1:100 individuals. Despite the frequency of the disease only a limited number of studies have been performed on clinical presentation, determinants of bleeding phenotype and Quality of Life (QoL). Therefore we have initiated a nationwide study on moderate and severe VWD in the Netherlands, the Willebrand in the Netherlands study, the WiN study.