Basing on roentgenological and morphological investigations the causes of the iliac veins passability disorder were studied up. In 45.1% of observations the stenosis was revealed of the left and in 1.2% of the right common iliac vein. Among the stenosis causes were osteal or cartilagenous prominences of vertebral column, intravascular structures (webs, membranes) in the left common iliac vein, the external iliac vein squeeze by internal iliac artery, retroperitoneal fibrosis, the right common iliac artery aneurysm, anomalous branching of parietal pelvic artery.