Diagnostic, prognostic and therapeutic applications of B-type natriuretic peptides (NPs) will probably become part of routine management of heart failure within five years. Cardiac release of NPs rises with increasing cardiac dysfunction. Their secretion and plasma levels respond to intracardiac distending pressures, with other modulating influences including age, sex, renal function and other aspects of neurohormonal status. Single and serial plasma NP measurements, particularly of B-type and N-terminal pro-B-type NP, show promise in diagnosis of heart failure, risk stratification in those with known heart disease, and in adjustment of anti-failure therapy. Recombinant B-type NP is an effective parenteral treatment in decompensated heart failure. These applications of B-type NPs require confirmation before they become established in routine management of heart failure.