Heart failure is a major public health problem and despite significant advances in treatment remains the only cardiovascular disease still on the rise. Because this patient population often has a number of other concomitant diseases, including hypertension, coronary artery disease, arrhythmias, diabetes, chronic obstructive pulmonary disease, and renal insufficiency, diagnosis can be difficult. Currently, diagnosis of acute decompensated heart failure (ADHF) relies largely on patient history, signs, and symptoms. Rapid and accurate diagnosis of ADHF in the emergency department (ED) is essential for timely initiation of treatment. Thus, any means for improving the speed and accuracy of ADHF diagnosis in the ED can contribute to better clinical and economic outcomes. Measurement of circulating endogenous B-type natriuretic peptide (BNP) has proven to be a sensitive and specific test for heart failure that can easily be used in the ED. Used in conjunction with standard diagnostic procedures, measurement of BNP levels can improve the accuracy of ADHF diagnosis during the critical window for optimal care.