Congestive heart failure (CHF) continues to be a major cause of morbidity and mortality; in the United States alone, CHF afflicts 4 million patients, representing about 2% of the adult population; causes or contributes to more than 250,000 deaths yearly; and is the principal or secondary diagnosis in 6% of all hospital discharges. After the discovery of angiotensin-converting enzyme (ACE) inhibitors as potent antihypertensive agents, an increased understanding of the pathophysiology of CHF, in addition to the recognition of heart failure as a process that evolves through time, led to the use of these agents in patients with CHF. Subsequently, a series of multicentertrials systematically explored the role of ACE-inhibitor therapy in heart failure. The purpose of this review is to discuss some of these trials and to describe the answers that they provide to the following questions: Are vasodilators beneficial in the treatment of severe heart failure? Are ACE inhibitors beneficial in mild-to-moderate heart failure? Which vasodilator regimen (ACE inhibitors or hydralazine/isosorbide dinitrate) is more effective? Finally, are ACE inhibitors beneficial in asymptomatic patients at risk of heart failure?