Several studies have reported increased von Willebrand factor (vWF) levels in plasma of uremic patients, with a normal multimeric pattern. Two recent studies, however, have shown a reduction of the larger multimers of plasma vWF and one has also found low levels of platelet vWF in uremic patients with prolonged bleeding time (BT). We have measured plasma and platelet vWF and analyzed its multimeric pattern in 20 uremic patients, 11 with a prolonged BT and 9 with a normal BT. For Plasma vWF, no difference for vWF:Ag, RiCof, and ristocetin-induced platelet agglutination was found between the two groups with normal and prolonged BT. The multimeric pattern of plasma vWF, as evaluated by densitometric scanning of the electrophoretic gels, was normal in both groups. For platelet vWF, vWF:Ag and RiCof content was similar in the two groups. The multimeric pattern was indistinguishable from that of normal platelets. In conclusion, our study does not confirm the presence of a structural defect of plasma vWF and the reduction of platelet vWF content in uremia. © 1993 Wiley-Liss, Inc.