In order to elucidate the prevalence of von Willebrand factor (vWF) deficiency state, we investigated plasma vWF levels among 343 patients with bleeding tendency, 465 patients without bleeding tendency and 704 random unrelated normals living in Kagoshima prefecture. The prevalence of symptomatic vWF deficiency state was at least 2.3 per 100,000 of the population, and that of asymptomatic one in healthy individuals was 1.3%. These results indicate that the overall incidence of vWF deficient state in general population would be considerably higher than that previously reported.