Finding a simple blood test to aid in the diagnosis and treatment of patients with congestive heart failure would have a favorable impact on the costs associated with the disease. B-type natriuretic peptide (BNP) is synthesized in the cardiac ventricles and correlates with left ventricular pressure, amount of dyspnea, and the state of neurohormonal modulation, making this 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 might serve as a screen for patients referred for echocardiography. A low BNP level makes echocardiographic indices of left ventricular dysfunction (both systolic and diastolic) highly unlikely. BNP may also be effective in improving in-hospital management of patients admitted with decompensated congestive heart failure. In some cases BNP levels may obviate the need for invasive hemodynamic monitoring and, when such monitoring is used, may help tailor treatment of decompensated patients. Finally, the role of BNP in outpatient cardiac or primary care clinics may be important in the titration of therapies and assessment of the state of neurohormonal compensation of patients.