Analysis of the multimeric structure of von Willebrand's factor (vWf) was compared with vWf-binding to collagen in subjects' plasma. The percentage binding of vWf to collagen was determined by both an enzyme-linked immunosorbent assay (ELISA) method and quantitative immunoelectrophoresis. Normal subjects, type I von Willebrand's disease (vWd), and type II vWd were studied. The authors have found by correlating collagen-binding results with multimeric analysis that normal controls exhibit 85.4 +/- 5.1% collagen absorption of their vWf, patients with type I vWd 80.8 +/- 5.3%, whereas patients exhibiting a deficiency of high molecular weight vWf have 32.3 +/- 16.6% collagen absorption of vWf. The results suggest that this functional assay of vWf can be used in the classification of vWd and in the detection of new dysfunctional forms of vWf.