Several large clinical studies have demonstrated the important benefit of mineralocorticoid receptor (MR) antagonists in patients with heart failure, left ventricular dysfunction after myocardial infarction, hypertension or diabetic nephropathy. Aldosterone adjusts the hydro-mineral balance in the body, and thus participates decisively to the control of blood pressure. This traditional view of the action of aldosterone restricted to sodium reabsorption in epithelial tissues must be revisited. Clinical and experimental studies indicated that chronic activation of the MR in target tissues induces structural and functional changes in the heart, kidneys and blood vessels. These deleterious effects include cardiac and renal fibrosis, inflammation and vascular remodeling. It is important to underscore that these effects are due to elevated MR activation that is inadequate for the body salt requirements. Aldosterone is generally considered as the main ligand of MR. However, this is a matter of debate especially in heart. Complexity arises from the glucocorticoids with circulating concentrations much higher than those of aldosterone, and the fact that the MR has a high affinity for 11β-hydroxyglucocorticoids. Nevertheless, the beneficial effects of MR inhibition in patients with heart failure emphasize the importance of this receptor in cardiovascular tissue. Diverse experimental models and strains of transgenic mice have allowed to dissect the effects of aldosterone and the MR in the heart. Taken together experimental and clinical data clearly highlight the deleterious cardiovascular effects of MR stimulation.