BACKGROUND Traditionally, venography is used to investigate deep vein thrombosis (DVT), though duplex ultrasound offers a challenging, noninvasive alternative method and previous reports have described the use of duplex ultrasound for detecting proximal lesions. OBJECTIVE To compare duplex ultrasound imaging with venography for both proximal and distal lesions using the probe compression technique and a different protocol. METHODS Duplex scans were done by the same operator prior and blind to venography, which was performed using a standard protocol with the films being reviewed blindly by a second radiologist at a later date. RESULTS In 74 patients, 21 of 22 above-knee lesions present on venography were detected by duplex scanning and there was complete agreement in the 52 of 52 venogram negatives. For lesions below the knee, duplex detected 26 of 27 lesions also present on venography and agreed on 37 of 43 venogram negatives. These figures give duplex ultrasound overall accuracies of 99% and 90% (Kappa 98% and 89%) for above- and below-knee lesions, respectively. CONCLUSIONS These figures suggest duplex ultrasound technique compares favorably with venography for diagnosing both proximal and distal lesions.