Intravascular ultrasound imaging is a relatively new imaging modality that uses miniaturized ultrasound transducers, which are mounted on catheter tips and introduced into the vessel lumen to provide cross-sectional images of the vascular structure in real time. It has gained popularity rapidly among interventional cardiologists because of its ability to overcome many limitations of angiography, especially when dealing with complex anatomy and new devices for coronary revascularization. The tomographic perspective and the ability to elicit the detailed structure of the arterial wall have allowed the use of intravascular ultrasound to better understand the coronary atherosclerotic and allograft vasculopathy disease processes. The response of lesions to various interventional procedures also has been studied in detail. This review discusses the rationale, technique, methods of interpretation, and the current knowledge in the field of intravascular ultrasound imaging.