Over the last years a growing interest for the biochemical abnormalities detectable in heart failure has become evident. In particular, large scientific evidence has been provided on hormones (catecholamines, renin–angiotensin–aldosterone system, natriuretic peptides) and cytokines (tumour necrosis factor, interleukins, etc.). Quite recently the attention of clinicians and researchers has also been directed towards high serum levels of tumour markers in this syndrome. Carbohydrate antigen 125 has been observed to increase in patients with congestive heart failure, to correlate with haemodynamic and clinical parameters of severity, and to show significant changes after adequate treatment. The aim of this paper is to review the data currently available on serum levels of tumour markers in patients with chronic heart failure, focusing the attention on the potential clinical use of carbohydrate antigen 125.