The recognition that patients with congestive heart failure often have elevated peripheral vascular resistance led to the introduction of vasodilator therapy. Of the vasodilators, the angiotensin-converting enzyme (ACE) inhibitors appeared to be the most promising because they had been shown to counteract some of the major adverse hormonal and vasoconstrictor mechanisms, relieve symptoms, diminish cardiac dilatation after myocardial infarction, and improve exercise capacity and ejection fraction.