Intravascular ultrasound (IVUS) is a new technique of tomographic visualization of the coronary arteries: its lumen, wall and pathology. Three dimensional (3D) reconstruction shows the tubular structure of the arterial wall and its pathology. IVUS has many advantages over coronary angiography: it has better resolution and shows many hidden lesions. IVUS has helped uncover the underlying mechanisms of percutaneous transluminal coronary angioplasty (PTCA), restenosis, the use and value of other interventional techniques such as directional coronary atherectomy (DCA), rotational atherectomy and stent implantation, and has great value in planning complex interventional procedures. The new American Heart Association (AHA) classification of coronary atherosclerosis pathology can be demonstrated by IVUS. IVUS is sensitive for studies of atheroma regression and progression and shows the coronary artery lesions after cardiac transplantation.