The most prominent components of the neuroendocrine response in heart failure are the catecholamines, the renin-angiotensin system, endothelin, and the atrial (ANP) and brain (BNP) natriuretic peptides. Their potential clinical applications include: (i) use as markers in the diagnosis of heart failure and in the screening of asymptomatic left ventricular dysfunction; (ii) use as predictors of specific cardiac events, including death; and (iii) use in tailoring and following up the treatment of heart failure patients. Until now, the major impediment that has put off the use of neuroendocrine assessment in clinical practice has been the lack of availability of reliable and cost-effective assay techniques, but this problem seems to be on the verge of being resolved as far as the natriuretic peptides are concerned...