Chronic venous insufficiency (CVI) is responsible for significant morbidity and health expenditure. Doppler ultrasound techniques provide a noninvasive method for identifying structural and functional abnormalities associated with CVI; this information then allows treatment options to be considered. Ultrasound allows clear identification of specific venous segments and provides information on the patency of these segments, the presence or absence of reflux, perforator veins, collateral channels, or patterns of recurrence after surgery. Techniques for the assessment of the lower limb veins are described, as are the techniques for the elicitation and quantification of reflux.