Ultrasonic Imaging provides a non-invasive assessment of the arterial and venous circulation in the lower limb and is accepted as a valuable diagnostic technique. Grey-scale images identify plaque and thrombus, duplex assessment provides a measurement of blood velocity through a vessel, and colour Doppler imaging enables the rapid localization of arterial stenoses and occlusions and the identification of incompetent veins. This article outlines the principles of the different techniques and presents normal images. Procedures for investigating arterial stenoses, superficial venous incompetence and deep venous thrombosis are described, abnormal images presented and the limitations discussed. It is hoped to provide an insight into the strengths and limitations of ultrasonic vascular investigations for those involved in tissue viability and ulcer management.