Intravascular ultrasound (IVUS) is a new imaging modality for the study of cardiovascular disease, which enables us to visualize the structure of the wall and the inner surface of the vessel. The instrument consists of a small very high frequency ultrasound transducer (12.5-40 MHz) mounted on the tip of a catheter, which can be introduced into the vessel. By rotating either the transducer itself or a mirror situated proximal to the transducer, cross-sectional images of the vessel wall with a high resolution are obtained. IVUS can distinguish between the different layers of the vessel and between different kinds of atherosclerotic plaques. Furthermore, the changes created by various interventional procedures may be visualised. These qualities of IVUS begin to comply with the rising demands for a better assessment of the results of the interventions--demands that cannot be fulfilled by arteriography. Moreover, IVUS may contribute to vascular diagnostics without the use of x-ray and contrast media, but is limited by its invasive nature and, until now, high costs.