Von Willebrand's disease is a familial hemorrhagic condition. There is no single test for diagnosis, no agreement on the pathogenesis, and no evidence as to the genetics of inheritance. Seven abnormalities have been reported to characterize the disease: prolonged bleeding time, capillary abnormality, thrombocytopathy, reduced blood-clotting factor VIII levels in the plasma, overresponse of factor VIII to transfusion, and reduced platelet adhesiveness both in vivo and in vitro. Generally, the triad of prolonged bleeding time, reduced platelet adhesiveness, and reduced plasmatic factor VIII characterizes the typical case, although some believe that the patient's factor VIII response to transfusion is the most important single finding.