Angiotensin II type 1 receptor blockers have favourable effects on haemodynamic measurements, neurohumoral activity, and left-ventricular remodelling when added to angiotensin-converting-enzyme (ACE) inhibitors in patients with chronic heart failure (CHF). We aimed to find out whether these drugs improve clinical outcome. Between March, 1999, and November, 1999, we enrolled 2548 patients with New York Heart Association functional class II-IV CHF and left-ventricular ejection fraction 40% or lower, and who were being treated with ACE inhibitors. We randomly assigned patients candesartan (n=1276, target dose 32 mg once daily) or placebo (n=1272). At baseline, 55% of patients were also treated with beta blockers and 17% with spironolactone. The primary outcome of the study was the composite of cardiovascular death or hospital admission for CHF. Analysis was done by intention to treat. The median follow-up was 41 months. 483 (38%) patients in the candesartan group and 538 (42%) in the placebo group experienced the primary outcome (unadjusted hazard ratio 0.85 [95% CI 0.75-0.96], p=0.011; covariate adjusted p=0.010). Candesartan reduced each of the components of the primary outcome significantly, as well as the total number of hospital admissions for CHF. The benefits of candesartan were similar in all predefined subgroups, including patients receiving baseline beta blocker treatment. The addition of candesartan to ACE inhibitor and other treatment leads to a further clinically important reduction in relevant cardiovascular events in patients with CHF and reduced left-ventricular ejection fraction.