Technical improvements in duplex ultrasound allow visualization of peripheral, cerebral and abdominal vessels with excellent quality. The resolution of so-called « high-end » ultrasound machines is even higher than computed tomography (CT) or magnetic resonance imaging (MRI) especially for superficial structures using high-frequency transducers. In addition to the quality of the machine and the skills of the sonographer, it is crucial to know the correct indication for the investigation and to ask the right questions. It seems simple but it requires knowledge of the disease and the diagnosis. In summary, it is essential to know exactly the patient’s history, symptoms and non-invasive clinical measurements (ankle–brachial index [ABI], for example) in order to correctly interpret findings of duplex ultrasound.