The pathophysiological condition, in which combined cardiac and renal dysfunction amplifies a progression in the failure of the individual organ, has been denoted as severe cardiorenal syndrome (SCRS). An interactive network of cardiorenal connectors, i.e., the renin-angiotensin system (RAS), nitric oxide (NO) and reactive oxygen species (ROS) balance, the sympathetic nervous system (SNS), and inflammation, has been proposed as the cornerstones of the pathophysiology of SCRS. Because erythropoietin (Epo) production declinesin chronic renal failure (CRF) and Epo sensitivity might decrease by the cardiorenalconnectors in patients with the SCRS, it is not surprising thatanaemia is a commonly occurring state coinciding with CRF and chronic heart failure (CHF). Epo treatment in patients with SCRS acts via haematopoietic effects, but also may intervenes in the vicious circle of cardiorenal connectors with subsequent deteriorating effects on cardiac, renal, and vascular function. It appears that regular Epo treatment in anaemic patients with diminished renal function improves cardiac performance, delays the progression of kidney disease, and may be of clinical benefit even to patients suffering from CHF with relatively mild anaemia. Despite growing evidence about Epo having positive effects on both renal and cardiac function, little is known about the underlying mechanisms of action.