In seven patients with acquired von Willebrand's disease (AvWD) associated with lymphoproliferative disorders or benign monoclonal gammopathies, the platelet contents of von Willebrand factor antigen and ristocetin cofactor (vWF:Ag and vWF:RiCof, respectively) were normal. All the multimers of vWF:Ag could be seen in the 1.6% SDS-agarose gel electrophoresis patterns of plasma and platelet lysates. Infusion of 1-deamino-8-D-arginine vasopressin (DDAVP) augmented plasma levels of vWF:Ag and vWF:RiCof of all patients and corrected prolonged bleeding times (BT). However, compared with patients with congenital vWD type I and comparable degrees of baseline abnormalities treated in the same way, vWF:Ag and vWF:RiCof were increased less and cleared more rapidly from plasma and the BT remained normal for a shorter period of time. These studies provide evidence that these AvWD patients have qualitatively normal vWF in plasma, but at lower concentrations, that vWF in platelets is normal both qualitatively and quantitatively, and that cellular vWF can be rapidly released into plasma by DDAVP to correct the hemostatic abnormalities. However, vWF is removed rapidly from plasma, making the correction more transient than in congenital vWD type I.