When patients have chest pain, their physicians can have difficulty deciding whether it is a sign of disease in the blood vessels around the heart, called coronary artery disease (CAD). To evaluate the risk for CAD, physicians can use information gained from studies of large groups of patients, knowing that older persons, men, smokers, and diabetic persons have a higher risk for CAD. Physicians can also obtain heart tracings (electrocardiograms) or stress tests that can indicate signs of damage or a problem with the heart's blood supply. However, many patients still go through a costly and somewhat risky test called coronary angiography (in which a catheter is placed through a blood vessel in the arm or groin to examine blood vessels around the heart with dye) but are found not to have CAD, whereas others are found to have CAD despite few signs or risk factors. Therefore, better approaches are needed to identify patients with chest pain who are more likely to have CAD. Analysis of a patient's genes may be a useful tool to help distinguish patients with CAD.