Congestive heart failure poses significant challenges to physicians with both diagnosis and management. B-type natriuretic peptide (BNP) is synthesized in the cardiac ventricles. It correlates with ventricular function, NYHA classification, and prognosis. It is extremely useful in the emergency department in patients presenting with acute dyspnea. It has a particularly strong negative predictive value. In addition, it should be important in screening patients for heart diease, either for those who are at high risk (chemotherapy, diabetes) or as a possible screen before echocardiography. In the future, BNP may be used to modulate treatment of patients in the decompensated setting as well as in titrating outpatient therapy.