Angiodynography of the pelvic and deep leg veins was compared with ascending phlebography in a prospective study, comprising 102 examinations. Improved detection of flow following the introduction of the so-called "slow flow technique" permitted direct visualisation of the tibio-fibular veins in the second stage of this study (26 examinations). Demonstration or exclusion of femoro-popliteal thrombosis achieved a sensitivity of 95% and 90% respectively and a specificity of 99% and 97%. During the first part of this study, demonstration of calf vein thrombosis had a low sensitivity of 72%. This was improved by the introduction of a new high-pass filter resulting in the detection of all occlusions (nine). The sonographic signs of acute and chronic occlusions overlap somewhat. Colour demonstration showed eccentric, non-linear channels in two out of three cases and was able to exclude thrombus, although the veins could not be compressed.