This study considered if N-terminal prohormone brain natriuretic peptide (NT-proBNP) is associated with increased risk for postoperative cardiac events in high-risk patients undergoing noncardiac surgery. In addition, this report describes how levels of NT-proBNP are affected by noncardiac surgery. The study design was a prospective cohort study that enrolled 83 patients age > or =50 years with > or =1 risk factor for coronary artery disease having intermediate or high-risk noncardiac surgery. NT-proBNP levels were measured preoperatively and on postoperative days 1 and 3. During the month following surgery, 25 patients (33%) had a combined 37 postoperative cardiac events including 15 episodes of heart failure (20%), 12 episodes of new dysrhythmia (16%), 7 myocardial infarctions (9%), and 3 cardiac arrests (4%). Preoperative NT-proBNP level > or =457 pg/ml was significantly associated with occurrence of a postoperative cardiac event (odds ratio 10.5, 95% confidence interval 1.9 to 56.6, p = 0.006). After surgery, 64 of 72 patients (89%) had an increase in NT-proBNP from their preoperative level. In conclusion, this study determined there was a significant association between elevated preoperative NT-proBNP and occurrence of a postoperative cardiac event. In addition, increased NT-proBNP after noncardiac surgery is not uncommon even in the absence of clinically identifiable heart failure.