The use of ultrasound contrast agents for peripheral vascular imaging has not been adapted widely worldwide and remains experimental in the United States. Nevertheless, there is considerable interest in contrast agents, because they potentially might offer substantial benefits for peripheral vascular imaging. This article reviews the status of ultrasound contrast agents. It includes a thorough discussion of the types of agents that are available or are under development and an assessment of the desirable properties of an ideal contrast agent. The interaction of these agents with ultrasound is considered next, including consideration of the advantages of harmonic imaging with contrast. Finally, the potential clinical benefits of contrast, as revealed by the authors experience and published data, are reviewed for a variety of cerebral, peripheral, and abdominal vascular applications. These include the carotid arteries, transcranial Doppler, extremity arteries and veins, the renal arteries, and hepatic vessels.