Previous attempts to identify predictors of cardiac complications, an important cause of postoperative morbidity and mortality following non-cardiac surgery, have focused mainly on the patient's preoperative state. Our research group, however, has found that adverse cardiac outcome correlates most highly with the appearance of at least 1 ischemic episode determined by continuous ambulatory electrocardiographic monitoring (AEM) in the early postoperative period. Such early postoperative ischemia conferred (1) a greater than 9-fold increased risk of experiencing in-hospital cardiac death, nonfatal myocardial infarction, or postoperative unstable angina, and (2) a greater than 2-fold increased long-term (2-year) risk of cardiac death, myocardial infarction, or angina requiring coronary angioplasty or coronary artery bypass grafting (CABG). Additionally, 5 predictors of such postoperative ischemia were identified: left ventricular hypertrophy, diabetes mellitus, hypertension, definite coronary artery disease, and preoperative digoxin use. These findings suggest that patients who are at high risk for postoperative myocardial ischemia warrant more intensive postoperative monitoring. Moreover, since such ischemia is potentially reversible, the testing of strategies designed to prevent or manage postoperative ischemia appears warranted and is discussed. Our group also has established the usefulness of AEM for identifying ischemic episodes in patients undergoing CABG. However, patients who require cardiopulmonary bypass present unique problems regarding the interpretation of AEM recordings. We describe guidelines for the interpretation of AEM results obtained under these conditions and suggest criteria based on the degree of interpretability for patient inclusion in future studies.