Based on 1234 examinations made by radionuclide venography the authors evaluated a group of 11 patients, where an occlusion of the vena cava was proved. In five instances ascension of thrombosis from the area of the pelvic veins was involved. in three instances compression by a tumour, twice the cause of occlusion was surgical ligature of the vena cava inferior. In one instance suppurative thrombosis developed as a result of spread of the infection from an intraabdominal abscess. Radionuclide venography provided evidence of a collateral circulation, as a rule a combination of several collateral routes was involved. Most frequently parietal collaterals in the abdominal aorta were present (9X), 4X paravertebral venous routes and only once anastomoses into the system of the azygos vein. In six patients anastomoses via the portal vein were found (cavoportal anastomoses). Based on their own experience, the authors evaluated the importance of radionuclide venography. Its advantage is the possible administration of the radiopharmaceutical preparation into the peripheral vein on the leg, the simple, safe procedure, the reproducibility and diagnostic yield during detection of high occlusions in the area of the vena cava inferior.