A previously healthy elderly man with gastrointestinal bleeding was found to have criteria for von Willebrand's disease. The late clinical onset of the disorder and negative family studies suggest that the von Willebrand's disease may be acquired. The findings in the patient were similar to the abnormalities reported in the small number of other patients thought to have acquired von Willebrands disease. An inhibitor of factor VIII could not be demonstrated in this patient. This patient also had platelet aggregation abnormalities that are atypical for patients with congenital or acquired von Willebrand's disease. Vascular abnormalities were also found in this patient and in several other previously described patients with von Willebrand's disease.