A 60-year-old woman with livedo reticularis was examined for defective release of vascular plasminogen activator by a newly described chromogenic assay. Her activator level was only 0.007 Committee on Thrombolytic Agents (CTA) units/mL, compared with a mean of 0.19 CTA units/mL for 84 female controls. Subsequently, the patient died as a result of thrombosis of the portal, splenic, hepatic and superior mesenteric veins with small-bowel infarction. The patient's family had a history of deep and superficial vein thrombosis. Her family's medical history was similar to a recently described pedigree, with low levels of releasable plasminogen activator associated with venous thrombosis. We believe that mesenteric vein thrombosis is a serious potential consequence of defective release of vascular plasminogen activator.