A multicenter study of various types of von Willebrand's disease (vWD) was conducted in order to compare the different electrophoretic techniques used to evaluate von Willebrand factor multimers in plasma. Seven laboratories participated in the blind study of eight plasma samples from two healthy subjects and six vWD types and subtypes (Ia, Ib, IIA, IIB, IIC and IID). From the results of the multimeric analysis of these samples, it appears that the differential diagnosis of vWD types and subtypes should be first approached by using a low-resolution electrophoretic technique, where each vWF multimer appears as a single band. Low-resolution techniques differentiate type I from type II, subtype Ia from Ib and also subtype IIA from other type II subtypes. When type II subtypes other than IIA are identified with these techniques, samples should be rerun using high resolution techniques that resolve each of the fastest migrating multimers in at least three subbands, and permit the differentiation of subtypes IIB, IIC and IID.