The role of intralesional coronary calcification is not only an important prognostic factor with respect to interventions, but can be extremely important with respect to diagnostic classification of lesion subsets. Intravascular ultrasound details the relationship between plaque and vessel wall in real time throughout the coronary arterial tree. This provides the opportunity to exactly define not only the quantity but also the distribution of calcium within the vessel wall. This is particularly important from a diagnostic standpoint, as plaque-containing calcification can often lead to ambiguous or erroneous angiographic information. Being able to classify different plaque substructures with intravascular ultrasound can help not only to clarify the ambiguous angiogram but delineate the exact nature of luminal encroachment. From a treatment standpoint, the identification of calcification patterns, particularly those on the superficial intimal surface, can alert the operator to change the compliance prior to definitive therapy. High-speed rotational atherectomy is a technique that provides significant de-calcification in preparation for optimizing the stent geometry within such lesion subsets. Although electron beam computed tomography can accurately locate calcification patterns within the coronary tree in a non-invasive manner, it's often difficult to know the extent of calcification and the relationship to fibrofatty plaques. Intravascular ultrasound albeit invasive, provides the opportunity to delineate these plaque substructures and potentially identify lesion subsets that may have an important natural history in the development of coronary atherosclerosis.