Angiotensin-converting enzyme inhibitors are mixed vasodilators with a prolonged sustained effect in chronic heart failure. They also act on the reactivity of peripheral circulation, on ventricular remodelling after myocardial infarction, on myocardial hypertrophy in arterial hypertension and on ventricular hyperexcitability. They alleviate the symptoms of symptomatic heart failure, and they constitute the only treatment that has been able to improve the survival of patients with the most severe heart failure. Several studies are in progress to determine whether these drugs should be used as first-line therapy.