Ultrasound contrast agents (US-CA) amplify reflected sound waves. Most substances used as contrast agents are destroyed when passing the lungs. SH U 508 is a new US-CA that can pass the lungs without impairment after peripheral intravenous application. In a clinical trial of this US-CA, we investigated its effect on the visualization of blood movement in peripheral arteries by color-coded Duplex sonography (CCDS). The leg arteries of 20 patients with severe chronic arterial occlusion were examined by CCDS (QAD I and Platinum) after i.v. application of the US-CA. After passage of the pulmonary capillaries, the US-CA amplified blood flow signals in the arterial system in a dose-dependent manner with both systems used. Undesired side-effects were not observed. The amplification produced by appropriate concentrations of the US-CA markedly improved the visualization of blood movement. Further studies are required to determine the optimal dosage and application technique as well as the indication for using this US-CA.