Measurable B-type natriuretic peptides (BNPs), which are largely produced by the left ventricle, include BNP and N-terminal prohormone BNP (NT-proBNP). These proteins are released by cardiomyocytes in response to wall tension and neurohumoral signals, and are established tools in the diagnosis and prognosis of heart failure (HF). We identified 32 articles for entry into evidence tables that presented original data on BNP and/or NT-proBNP in more than 100 patients with acute coronary syndromes (ACS) presenting with chest discomfort with or without dyspnea. Natriuretic peptide (NP) elevation was associated with older age, female sex, hypertension, diabetes, prior HF, prior ischemic heart disease, and reduced renal function. Clinical correlates of elevated blood NP levels included left main or 3-vessel coronary disease, lipid-rich plaques with large necrotic cores in proximal locations, large zones of myocardial ischemia or infarction, no-reflow and impaired perfusion after percutaneous intervention, reduced left ventricular ejection fraction, higher Killip classification, and the development of cardiogenic shock. All studies indicated that after adjustment for baseline predictors and clinical risk scores, elevated NP concentrations were independently predictive of the development of HF and all-cause mortality. In contrast, studies did not consistently demonstrate that NPs were predictive of myocardial infarction and rehospitalization for ACS. In addition to baseline measurement, there is consensus that repeat testing at 4 to 12 weeks and 6 to 12 months in follow-up is helpful in the anticipation of late cardiac sequelae and may assist in assessing prognosis and guiding management.