(1) Some angiotensin-converting-enzyme inhibitors (ACE inhibitors) reduce mortality in patients with heart failure (captopril, enalapril, ramipril and trandolapril), and in patients with recent myocardial infarction and heart failure or marked left ventricular dysfunction (captopril, ramipril and trandolapril). (2) Angiotensin II receptor antagonists, otherwise known as angiotensin receptor blockers, have haemodynamic effects similar to ACE inhibitors, but differ in their mechanism of action and certain adverse effects. (3) Five clinical trials have evaluated angiotensin II receptor antagonists (candesartan, losartan and valsartan) in terms of their effect on mortality and on the risk of clinical deterioration in patients with symptomatic heart failure, but without severe renal failure, hyperkalemia or hypotension. In these trials, candesartan and valsartan were used at much higher doses than those recommended for the treatment of arterial hypertension. (4) In patients with heart failure who were not taking an angiotensin II receptor antagonist or an ACE inhibitor at enrollment, no significant difference was found between losartan and captopril in terms of mortality or the risk of clinical deterioration. (5) In patients with heart failure who had stopped taking an ACE inhibitor because of adverse effects, candesartan had no effect on mortality as compared with placebo, but it did reduce the risk of clinical deterioration (3 fewer hospitalisations per year per 100 patients). However, candesartan was associated with adverse effects such as renal failure and hyperkalemia, especially in patients who had experienced these same adverse effects while taking an ACE inhibitor. (6) In patients with heart failure who were already taking an ACE inhibitor, adjunctive candesartan or valsartan treatment did not influence mortality in comparison to the addition of a placebo. Adding candesartan or valsartan reduced the risk of hospitalisation (between 1 and 3 fewer hospitalisations per year per 100 patients), but increased the risk of renal failure and hyperkalemia. (7) In patients with heart failure and incapacitating dyspnea despite ACE inhibitor + diuretic combination therapy, there are no trials comparing the addition of an angiotensin II receptor antagonist versus spironolactone. Adjunctive spironolactone therapy prevents 5 to 6 deaths per year per 100 patients in this setting. (8) In patients with heart failure who do not have markedly altered cardiac contractility, candesartan appears to have no clinical advantages over placebo. (9) In some of these trials, mortality was higher with angiotensin II receptor antagonist therapy than with placebo among patients who were already taking a betablocker. (10) Two trials have compared an angiotensin II receptor antagonist with an ACE inhibitor in patients with recent myocardial infarction who had heart failure or an altered left ventricular ejection fraction, but who did not have hypotension or severe renal failure. However, there are no placebo-controlled randomised trials assessing the effects of angiotensin II receptor antagonists on mortality. (11) In patients with recent myocardial infarction, these trials showed no difference in mortality between angiotensin II receptor antagonist treatment (losartan or valsartan) and captopril. They did not rule out the possibility that these angiotensin II receptor antagonists are moderately less effective than captopril. Adding valsartan to ongoing captopril therapy did not reduce mortality or morbidity as compared with placebo, but did increase the risk of adverse effects. (12) Overall, these trials confirm the advantage of angiotensin II receptor antagonists over ACE inhibitors with respect to some adverse effects (cough, skin rash, etc.). However, the two drug classes share certain serious adverse effects such as hyperkalemia, renal failure and hypotension. In one trial, angioedema was less frequent with angiotensin II receptor antagonist therapy (one less case per 500 patients).