Finding a simple blood test to aid in the diagnosis and treatment of patients with congestive heart failure could have a favorable impact on the costs associated with the disease. B-type natriuretic peptide (BNP) is synthesized in the cardiac ventricles, and its level correlates with left ventricular pressure, amount of dyspnea, and the state of neurohormonal modulation, thus making peptide the first potential "white count" for heart failure. Data indicate that serial point-of-care testing of BNP should be helpful in patients presenting to urgent care clinics with dyspnea. BNP may also serve as a screen for patients referred for echocardiography. A low BNP level makes left ventricular dysfunction (both systolic and diastolic) highly unlikely. BNP may also provide an effective means of improving in-hospital management of patients admitted with decompensated congestive heart failure. In some cases, BNP level observations may obviate the need for invasive hemodynamic monitoring and, when such monitoring is used, may help tailor treatment of the decompensated patient. Finally, the role of BNP in the outpatient cardiac or primary care clinic may be one of critical importance in titration of therapies as well as in assessing the state of neurohormonal compensation of the patient.