The measurements of B-type natriuretic peptide (BNP) or N-terminal proBNP (NT-proBNP), when taken together with conventional clinical assessment, may assist in making the prognosis and also for making serial adjustment of such treatment. But although such commercial assays are currently approved for the diagnosis of heart failure, the role of the natriuretic peptides for monitoring the success of congestive heart failure (CHF) therapy has not as yet been submitted for regulatory approval. Moreover, because of the intra-individual biologic variation of the BNP or because of multiple factors that affect the BNP levels, the magnitude of the change of BNP levels must be large to confidently interpret BNP changes within an individual, and just how large has not been determined. Yet the levels of plasma BNP and NT-pro BNP are well correlated with the concurrent haemodynamic measurements and indicators of left ventricular systolic function. Also, BNP and NT-pro BNP serve as significant prognostic information and it is possible that adjustment of anti-heart failure therapy according to serial measurements of BNP (in addition to the standard clinical assessment) may offer improved outcomes. Better understanding of the test characteristics is needed before we can effectively use this valuable test to guide therapeutic strategies.