Based upon the results of the RALES trial and accumulating evidence about the role of aldosterone and aldosterone receptor antagonism in various disease states, the authors anticipate that aldosterone receptor antagonists will become standard therapy, along with ACE inhibitors and beta-adrenergic receptor blocking agents, in patients with heart failure that is caused by systolic left ventricular dysfunction. Furthermore, the prospect of the use of these agents in other disease states that have implicated an activated rennin-angiotensin-aldosterone cascade, such as diastolic dysfunction, aging, and atherosclerosis, remains to be tested. Until further data from well-designed, prospective, randomized trials are available, the use of aldosterone receptor antagonists should be restricted to patients with severe or progressive heart failure caused by systolic left ventricular dysfunction in whom serum creatinine level is < or = 2.0 mg/dL and serum potassium levels are < 5.0 meq/L at baseline.