The angiotensin converting enzyme (ACE) inhibitors constitute a major breakthrough in the medical management of congestive heart failure. The incidence of side effects with these agents is surprisingly low when they are used in the appropriate dosage. They produce sustained beneficial hemodynamic and symptomatic improvement in most patients with congestive heart failure and may produce greater symptomatic benefit than digoxin when given as second-line therapy to patients with heart failure on diuretics. Their neurohumoral effects generally are advantageous, resulting in normalization of sodium and potassium balance and a reduction in ventricular arrhythmias. The ACE inhibitors may improve survival in patients with congestive heart failure, and recent data suggest that they may prevent or delay the development of left ventricular dilatation and overt heart failure in patients with asymptomatic left ventricular dysfunction.