Intravascular ultrasound (IVUS) is a dynamic imaging modality that provides real-time in vivo visualization of atherosclerosis and other vascular pathology. The tomographic image presentation of IVUS permits detailed assessment of plaque morphology and its corresponding responses to interventional therapy. IVUS studies have confirmed vascular remodeling in vivo, have proposed a high-pressure stent implantation strategy and have shown two key mechanisms of restenosis after angioplasty: plaque proliferation and vessel shrinkage (negative remodeling). IVUS also provides accurate quantitative information regarding lumen size, vessel size and plaque burden. These observations, essential to achieving improved outcomes, have drastically changed the understanding of atherosclerotic artery disease and interventional procedures. IVUS has matured into an essential complement to daily peripheral and coronary interventional practice and is routinely incorporated as part of the interventional arsenal in the catheterization laboratory. A variety of new imaging techniques are currently being designed and tested. These include combined therapeutic devices, further miniaturization, 3-D applications and tissue characterization. These techniques may evolve to provide increased favorable clinical outcomes and more accurate information of vessel geometry and plaque composition.