An intravascular ultrasound (IVUS) is a new cardiological diagnostic technique which provides detailed cross-sectional images of the vessel wall, allows to investigate lumen, as well as structure of the coronary artery. This imaging technique has the unique potential to provide an image of atherosclerotic plaque, characterizes its composition, and severity of stenosis. "Soft" plaque, dense fibrous "hard" plaque, calcification and thrombosis have all been identified using IVUS. Intravascular ultrasound imaging has become a method for supporting interventional decision making by selecting patients who are to undergo Percutaneous Transluminal Coronary Angioplasty, Stent placement, Directional Coronary Atherectomy or Laser Angioplasty. Quality of measurements should allow more widespread use to guide interventional techniques. A series of IVUS imagings could assess the influence of plaque composition on mechanism of immediate lumen enlargement after revascularization. With utilization of IVUS guidance and high pressure balloon inflation--stent implantation could now be performed "optimally" and safely without anticoagulation. This original diagnostic tool is becoming a clinically useful adjunct to angiography in the assessment coronary arteries of heart transplant recipient and patients with higher risk of restenosis.