The condition of the inferior vena cava system was studied in 597 patients after percutaneous implantation of the antiembolic cava-filter on the basis of the clinical findings and results of angiographic and pathoanatomical examination. The patency of the inferior vena cava was found to be maintained in the immediate postimplantation period in most patients. The causes of occlusion of the inferior vena cava in 10% of cases (according to the clinical findings) were embolic occlusion of the cava-filter and ascending thrombosis of the iliocaval segment.