Over a 2-year period the authors examined 400 patients affected with different types of phlebopathies with combined real-time US and pulsed Doppler (Duplex system). Ninety-eight patients had deep phlebothrombosis, 45 had superficial phlebothrombosis, and 110 primitive or secondary vein insufficiency. The obtained data, supported in 171 cases by contrastographic findings, allowed both the semeiological study and the evaluation of the indications for Duplex US in the various phlebopathies. The combination of high-resolution US morphological data, dynamic tests, and the functional data from pulsed Doppler have particular interest in the study of: a) the diagnostics of superficial or deep thrombosis and adhesive or floating thrombi; b) post-thrombotic syndrome; c) primitive or secondary vein insufficiency; d) the ostium of the superficial venous system (location, morphology, functionality). Duplex US is a non-invasive technique for the examination of the superficial and the deep venous systems, which reduces the indications for phlebography, an exam which requires radiation exposure, and is not always safe or possible. Duplex US is however limited by the difficult assessment of the venous system below the knee, because of too many trunks and variants.