Perioperative myocardial infarction is the most common cause of morbidity and mortality in cardiac surgery. It occurs in 8% to 35% of patients. The primary aim of this prospective study was to determine the level of cardiac troponin I that indicates perioperative myocardial infarction in patients undergoing coronary artery bypass. A secondary goal was to establish the best independent predictor of hospital death. There were 180 consecutive patients undergoing isolated coronary artery bypass surgery enrolled in this study. Values of cardiac troponin I > 12.9 ng.mL(-1) at 8 hours postoperatively predicted perioperative myocardial infarction with a sensitivity of 100% and a specificity of 93.2%. Compared to patients who survived, those who suffered hospital death were significantly older (74 +/- 7 vs 63 +/- 10 years), had significantly higher levels of cardiac troponin I at 24 hours (9 +/- 17 vs 27.3 +/- 16 ng.mL(-1)) and 48 hours (6.9 +/- 19 vs 30.3 +/- 24 ng.mL(-1)) postoperatively, and a significantly higher EuroSCORE (9 +/- 2 vs 4 +/- 3). At 8 hours postoperatively, cardiac troponin I led to an earlier diagnosis of perioperative myocardial infarction, while EuroSCORE was the strongest independent predictor of hospital death.