In patients with stable and unstable angina pectoris, the occurrence of transient ST-T-wave alterations during ambulatory electrocardiographic monitoring is helpful in identifying a subgroup of patients who are especially likely to have severe atherosclerotic coronary artery disease and a guarded prognosis over the subsequent 1 to 12 months. Because the majority of these episodes are not accompanied by chest pain, it seems logical to conclude that recurrent episodes of silent myocardial ischemia signal a high likelihood of severe coronary artery disease and carry a poor short-term prognosis.