Calcification is a common finding in human coronary arteries, which is generally associated with long-standing atherosclerosis. However, there is conflicting evidence for the link between calcification and plaque instability. Recent histopathological studies have revealed that plaque calcification is present in 69% of ruptured plaques in sudden coronary death. Furthermore, studies using electron-beam computed tomography have reported that calcium score relates to acute coronary events. Recently, we clarified that in patients with acute myocardial infarction small "spotty" calcifications prevailed, associated with a fibrofatty plaque and positive remodeling. Future studies would focus on the clinical implication of coronary calcification.