BACKGROUND AND MORPHOLOGIC STUDIES: Because coronary artery calcification correlates highly with plaque burden, it is an excellent disease marker for atherosclerosis. However, it is not a sensitive indicator of disease activity, and does not predict luminal compromise because of compensatory remodeling. In addition, most data do not support the concept that plaque calcification is related to plaque instability. Plaques demonstrating acute rupture usually show mild or moderate calcification, and biophysical models do not predict that calcium should result in an increased propensity to rupture. This review outlines morphologic studies relating calcification to risk factors and coronary plaque morphology.