Duplex venous scanning is a new noninvasive modality useful in the diagnosis of deep vein thrombosis. Its use is demonstrated in a case study. The mobility of this technique allows the patient to be studied at his bedside even while in traction. The development of deep vein thrombosis and the course of its progression can be monitored utilizing the duplex scan. The course of treatment can be altered if necessary. A Greenfield vena caval filter was inserted following identification of a clot in the common femoral vein to prevent a pulmonary embolus. The accuracy of venous duplex scanning, together with its many advantages over other diagnostic techniques and its few disadvantages, makes this procedure the noninvasive study of choice for the diagnosis and management of acute deep vein thrombosis.