OBJECTIVES among patients undergoing noncardiac surgery, our objectives were to: (1) determine the feasibility of undertaking a large international cohort study; (2) estimate the current incidence of major perioperative vascular events; (3) compare the observed event rates to the expected event rates according to the Revised Cardiac Risk Index (RCRI); and (4) provide an estimate of the proportion of myocardial infarctions without ischemic symptoms that may go undetected without perioperative troponin monitoring. DESIGN An international prospective cohort pilot study. PARTICIPANTS Patients undergoing noncardiac surgery who were >45 years of age, receiving a general or regional anesthetic, and requiring hospital admission. MEASUREMENTS Patients had a Roche fourth-generation Elecsys troponin T measurement collected 6 to 12 hours postoperatively and on the first, second, and third days after surgery. Our primary outcome was major vascular events (a composite of vascular death [i.e., death from vascular causes], nonfatal myocardial infarction, nonfatal cardiac arrest, and nonfatal stroke) at 30 days after surgery. Our definition for perioperative myocardial infarction included: (1) an elevated troponin T measurement with at least one of the following defining features: ischemic symptoms, development of pathologic Q waves, ischemic electrocardiogram changes, coronary artery intervention, or cardiac imaging evidence of myocardial infarction; or (2) autopsy findings of acute or healing myocardial infarction. RESULTS We recruited 432 patients across 5 hospitals in Canada, China, Italy, Colombia, and Brazil. During the first 30 days after surgery, 6.3% (99% confidence interval 3.9-10.0) of the patients suffered a major vascular event (10 vascular deaths, 16 nonfatal myocardial infarctions, and 1 nonfatal stroke). The observed event rate was increased 6-fold compared with the event rate expected from the RCRI. Of the 18 patients who suffered a myocardial infarction, 12 (66.7%) had no ischemic symptoms to suggest myocardial infarction. CONCLUSIONS This study suggests that major perioperative vascular events are common, that the RCRI underestimates risk, and that monitoring troponins after surgery can assist physicians to avoid missing myocardial infarction. These results underscore the need for a large international prospective cohort study.