Von Willebrand's disease is an autosomally transmitted disorder of hemostasis caused by a deficiency of or defect in the von Willebrand factor in the blood, a protein required for adherence of platelets to an injured vessel wall. The disease's principal manifestations are spontaneous bleeding from mucous membranes, excessive bleeding from wounds, and menorrhagia. The major laboratory abnormality in prolongation of the skin bleeding time, with reduced platelet retention by glass bead columns, impaired platelet agglutination by ristocetin, and reduced factor VIII--related antigen and factor VIII coagulant activity as associated defects. Recommended therapy is infusion of plasma cryoprecipitate, which briefly corrects bleeding time and normalizes the disorder's other manifestations.