The application of intravascular ultrasound (IVUS) within the coronary arteries has allowed for an enhanced characterization of the size and distribution of atheroma and the natural history of the arterial wall's response to its accumulation. IVUS is performed safely at the time of diagnostic coronary angiography and involves the placement of a high frequency ultrasound transducer on the tip of a catheter within the major epicardial coronary arteries. IVUS has been used to estimate the extent of atheroma throughout segments of coronary arteries. The ability to visualize the entire arterial wall in vivo has allowed IVUS to be employed to characterize the accumulation of atherosclerotic plaque within the arterial wall. A continuous relationship was demonstrated between changes in low density lipoprotein (LDL) cholesterol and atheroma volume. IVUS has been employed to investigate the formation of neointimal hyperplasia in a range of clinical settings.