Aldosterone plays a key role in the pathophysiology of heart failure. Angiotensin converting enzyme inhibitors and angiotensin II receptor blockers may not suppress aldosterone production in the long term. This allows aldosterone to exert its effects on myocardial fibrosis and cardiac remodelling, endothelial function, electrolytes and baroreceptor response. The Randomized Aldactone Evaluation Study (RALES) tested spironolactone against placebo in patients with severe heart failure. The study found a 30% reduction in the risk of death among patients treated with spironolactone and a 31% reduction in the risk of death from cardiac causes. Patients in the spironolactone group had significantly lower risks of death from progression of heart failure and sudden cardiac death. The Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS) investigated the effects of eplerenone against placebo in patients with myocardial infarction complicated by left ventricular dysfunction. Compared to placebo, the relative risk of death from any cause was 0.85 in eplerenone-treated patients, and the relative risk of death or hospitalisation for cardiovascular events was 0.87. The reduction in the risk of sudden death from cardiac causes was statistically significant. In conclusion, aldosterone blockade should form part of optimal therapy for patients with heart failure.