The success of angiotensin-converting enzyme (ACE) inhibitors in reducing morbidity and mortality in patients with heart failure has led to investigations of other inhibitors of the renin-angiotensin-aldosterone system. Although ACE inhibitors remain first-line drugs in the treatment of heart failure and left ventricular dysfunction, clinical evidence suggests that a newer class of agents--angiotensin II receptor blockers--may provide additional benefit by blocking the adverse effects of angiotensin II more completely. An improved adverse-effect profile also makes angiotensin II receptor blockers appropriate in patients who cannot tolerate ACE inhibitors. Clinical trials have demonstrated the beneficial effects of angiotensin II receptor blockers on the combined endpoints of morbidity and mortality in patients with heart failure. Aldosterone antagonism with spironolactone has additive benefits in patients receiving an ACE inhibitor. The most recent treatment guidelines for heart failure recommend the use of angiotensin II receptor blockers and spironolactone in selected patients.