The iliocaval compression syndrome is a disorder, frequently found in young women, in which extrinsic compression of the left iliocaval junction produces signs and symptoms of lower extremity venous insufficiency. The anatomic variant which gives rise to this syndrome consists of compression of the left common iliac vein by the overlying right common iliac artery, near its junction with the vena cava. Additional reduction of outflow results from intraluminal venous webs and tight adhesions between the iliac artery and vein. Pain, swelling, pigmentation, and venous claudication characterize this syndrome, which affects predominantly the left leg. The syndrome may progress to iliofemoral thrombosis, phlegmasia cerulea dolens, and venous gangrene. Longstanding iliocaval stenosis may produce valvular incompetence. Exercise plethysmography is a non-invasive test useful in screening patients for iliocaval compression. The definitive diagnosis is made by venography, both ascending and descending, to determine the degree of outflow stenosis. Iliocaval patch angioplasty with retrocaval positioning of the right iliac artery, decreases venous hypertension and leads to improvement in the clinical condition. To date, we have performed iliocaval angioplasty, with retrocaval repositioning of the right common iliac artery, on 18 patients. Of these, 83% have had good results as determined by hemodynamic and clinical assessment.