Calcification is a common finding in human coronary arteries. However, there is conflicting evidence for a link between calcification and plaque instability. Current intravascular ultrasound (IVUS) technology allows a definitive detection of the calcification and measurement of the vessel wall. Using preinterventional IVUS images, we clarified that in patients with acute myocardial infarction, small "spotty" calcifications prevailed, associated with a fibrofatty plaque and positive remodeling. Conversely, in patients with stable angina pectoris, extensive calcification was frequent. IVUS allows the detection of vulnerable plaques in coronary arteries, by identifying not only a large lipid core and positive remodeling, but also a spotty pattern of calcification.