The fact that the heart is able to secrete hormones, which are released in significant amounts in advance of certain cardiac conditions, has resulted in a wide range of opportunities and raised a multitude of questions. These hormones, named natriuretic peptides, possess diuretic, natriuretic and vasodilatory properties. The ones used in daily clinical practice are atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and their N-terminal fragments NT-proANP and NT-proBNP, respectively. Although most studies currently involve the use of BNP, the number involving NT-proBNP is expected to increase substantially in coming years because its level is less variable and its half-life longer. Nevertheless, at present there appears to be sufficient evidence to suggest that the plasma levels of these hormones will be extremely useful for the diagnosis, prognosis, screening, pharmacological monitoring, and treatment of patients with heart failure.