By using anti-human von Willebrand factor (vWF) monoclonal antibody, SZ-29, and indirect immunofluorescent technique and spectrofluorophotometer, we have quantitated platelet-bound vWF in normal subjects and patients with coronary heart disease (CHD). The results demonstrated that the quantity of platelet-bound vWF in CHD patients was significantly higher than that in normal (P less than 0.01) and the percentage of naturally activated platelet in CHD patients was also significantly higher than that in normal subjects (P less than 0.01). This might be one of the causes of hypercoagulability in CHD patients.