Summary. To get insights into the pathogenesis of acquired von Willebrand disease associated with plasma cell dyspasias, we searched for the expression of the physiological von Willebrand factor receptor, the GpIb/GpIX complex, on bone marrow plasma cells. The monoclonal spike in our patient corresponded to IgGκ molecules; there was no plasma inhibitor to vWF:Ag or vWF:RiCoF. The bone marrow contained 1–2% plasma cells. Fresh bone marrow cells or plasma cells enriched bone marrow cells after a 48 h in vitro culture in the presence of interleukin 6 were stained by an immuno alkaline phosphatase technique using monoclonal antibodies (mAb) to von Willebrand factor, GpIb α and β chain, GpIIb/IIIa and Gp IX. Two different mAb to GpIb α chains reacted with the majority (75%) of plasma cells whereas all other reagents yielded no staining. Malignant plasma cells from patients with multiple myeloma without haemostatic disorder were unreactive with anti-GpIb mAb. These data suggest that in some patients with acquired von Willebrand syndrome there is a GpIb mediated selective adsorption of von Willebrand factor on clonal plasma cells.