Background: Ivabradine specifically inhibits the If current in the sinoatrial node to lower heart rate, without affecting other aspects of cardiac function. We aimed to test whether lowering the heart rate with ivabradine reduces cardiovascular death and morbidity in patients with coronary artery disease and left-ventricular systolic dysfunction. Methods: Between December, 2004, and December, 2006, we screened 12 473 patients at 781 centres in 33 countries. We enrolled 10 917 eligible patients who had coronary artery disease and a left-ventricular ejection fraction of less than 40% in a randomised, double-blind, placebo-controlled, parallel-group trial. 5479 patients received 5 mg ivabradine, with the intention of increasing to the target dose of 7·5 mg twice a day, and 5438 received matched placebo in addition to appropriate cardiovascular medication. The primary endpoint was a composite of cardiovascular death, admission to hospital for acute myocardial infarction, and admission to hospital for new onset or worsening heart failure. We analysed patients by intention to treat. The study is registered with ClinicalTrials.gov, number NCT00143507. Findings: Mean heart rate at baseline was 71·6 (SD 9·9) beats per minute (bpm). Median follow-up was 19 months (IQR 16-24). Ivabradine reduced heart rate by 6 bpm (SE 0·2) at 12 months, corrected for placebo. Most (87%) patients were receiving β blockers in addition to study drugs, and no safety concerns were identified. Ivabradine did not affect the primary composite endpoint (hazard ratio 1·00, 95% CI 0·91-1·1, p=0·94). 1233 (22·5%) patients in the ivabradine group had serious adverse events, compared with 1239 (22·8%) controls (p=0·70). In a prespecified subgroup of patients with heart rate of 70 bpm or greater, ivabradine treatment did not affect the primary composite outcome (hazard ratio 0·91, 95% CI 0·81-1·04, p=0·17), cardiovascular death, or admission to hospital for new-onset or worsening heart failure. However, it did reduce secondary endpoints: admission to hospital for fatal and non-fatal myocardial infarction (0·64, 95% CI 0·49-0·84, p=0·001) and coronary revascularisation (0·70, 95% CI 0·52-0·93, p=0·016). Interpretation: Reduction in heart rate with ivabradine does not improve cardiac outcomes in all patients with stable coronary artery disease and left-ventricular systolic dysfunction, but could be used to reduce the incidence of coronary artery disease outcomes in a subgroup of patients who have heart rates of 70 bpm or greater. Funding: Servier, France.