The Doppler Ultrasonic Velocity Detector has been shown to be of significant value in the evaluation of patients with suspected deep venous thrombosis. Our experience in 121 patients demonstrates a false-negative rate of 10% for "minimal" thrombophlebitis and 3.2% for ileofemoral thrombosis when the Doppler was used as a diagnostic aid. Since ileofemoral thrombosis represents the greatest threat to the patient in terms of pulmonary embolism, this appears to be a sensitive and specific technic for the detection of ileofemoral thrombosis.