A serrated teflon clip for partially occluding the inferior vena cava to prevent pulmonary embolism has been used in the management of thromboembolic disease in 42 patients. Experimental testing of the device demonstrated that it trapped all emboli of 5 mm or larger diameter. Pulmonary angiography preoperatively was used in eight patients to confirm the clinical impression of embolism. Indications for the clip were formation of emboli in patients on anticoagulant therapy and others with contraindications to these drugs. There has been no operative mortality due to use of the clip nor postoperative pulmonary embolization following its application. Four patients who apparently had no further embolus formation after clipping were studied by postoperative venograms of the inferior vena cava and passage of a cardiac catheter through the clip site. The cava was patent in each.