In technique for lower extremity phlebography the patient is in a semi-upright position, supporting his weight on the contralateral foot. The dye injection is made into a dorsal pedal vein and no tourniquet is used. Fluoroscopy is used to maximize efficiency of the filming. More than 300 phlebograms have been made with this method. The four cardinal signs of phlebothrombosis are constant filling defects, abrupt termination of the dye column, nonfilling of the entire deep venous system or portions thereof, and diversion of flow. Pitfalls in interpretation occur when artifacts are created by bearing weight on the leg under study, by tourniquets, by an improper injection site, or by incomplete mixing of the contrast material as it flows through the veins.