While deficiency of a disintegrin and metalloprotease with thrombospondin-1-like domains (ADAMTS-13) was reported as the basis for the pathogenesis of thrombotic thrombocytopenic purpura (TTP), low levels have also been found in other thrombocytopenic disorders. This study was conducted to characterize the activity and antigen levels of ADAMTS-13 and von Willebrand factor (vWF) in patients with different thrombocytopenic disorders in Kuwait.