The cardiorenal syndrome (CRS) is defined as a complex pathophysiological disorder of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in the other. A new classification of CRS has been proposed with five subtypes that reflect the pathophysiology, the bidirectional nature of heart and kidney interaction and the time-frame. The pathophysiology of the CRS involves interrelated hemodynamic and neurohormonal mechanisms, including the renin-angiotensin- aldosterone system, the sympathetic nervous system, the imbalance between nitric oxide and reactive oxygen species, anemia, inflammation and others such as endothelin and arginine vasopressin system activation. CRS remains a challenge in treatment options. Traditional agents, including diuretics, angiotensin converting enzyme inhibitors/angiotensin receptor blocker, β-blockers and erythropoietin, are chosen to alleviate symptoms. Novel agents, such as adenosine A1 antagonists and vasopressin receptor antagonists, have been evaluated in randomized controlled trials. Renal replacement therapy should be used early if diuretic resistance exists.