Cardiorenal syndrome (CRS) describes the reciprocally detrimental interaction between both acute and chronic cardiac and renal dysfunction. The syndrome is prevalent and carries a high mortality. CRS has five clinical subtypes, which share common pathogenetic mechanisms including neurohumoral and haemodynamic derangements. We describe several serum markers that offer improvements over traditional measurement of serum creatinine for the diagnosis of CRS. The mainstay of therapy of CRS is loop diuretics in the acute setting and ACE-inhibition in the chronic setting, the latter should in most cases continue despite therapy-associated increases in creatinine. Extracorporeal therapies remain second line treatment.