Coronary artery disease affects 1,500,000 Americans each year; 500,000 of these will die. The earliest detectable lesion of coronary atherosclerosis is the fatty streak. Later, crescent-shaped lipid plaques occur, which may rupture and produce either progressive stenosis or sudden occlusion with myocardial infarction. Calcium is deposited early in the formation of the atherosclerotic plaque, and calcification can be used as a marker of the atherosclerotic process. Many imaging techniques can be used to detect calcification of coronary arteries. The most promising are fluoroscopy, ultrafast CT, and intravascular sonography. Detection of calcification is most valuable in persons less than 40 years old in whom modification of risk factors may be important. In addition, the progression and possible regression of calcification can be used as an indicator of the atherosclerotic process. The absence of calcification in coronary arteries may diminish the need for further testing.