Atherosclerosis causes various types of flow disturbances within the affected arteries. Recent advances in the Doppler imaging technique have made possible evaluation of the temporal and spatial flow characteristics in the different portions of the arterial system, such as aorta, coronary, carotid and peripheral arteries. In the diagnosis of dissecting aneurysm of the aorta, transesophageal Doppler color flow imaging is quite useful to detect the site of entry, which is essential information for surgery. Intracoronary flow velocity can be accurately measured by intravascular Doppler technique. The recent introduction of a Doppler-tipped angioplasty guide wire makes it possible to measure the phasic flow deep within a coronary artery. The flow velocity measurement using a duplex system enables us to quantify the stenotic severity in carotid and peripheral arteries, and the Doppler color flow imaging, which has become available recently, also facilitates the demonstration and grading of atheromatous lesions in these arteries.