BACKGROUND Conflicting results from recent observational studies have raised questions concerning the benefit of β-blockers for patients undergoing coronary artery bypass grafting (CABG). Furthermore, the efficacy of long-term β-blocker therapy in CABG patients after hospital discharge is uncertain. RESULTS The study included 5926 consecutive patients who underwent CABG and were discharged alive. The prevalence and consistency of β-blocker use were determined in patients with and without a history of myocardial infarction (MI). β-Blockers were always used in 1280 patients (50.9%) with and 1642 patients (48.1%) without previous MI after CABG. Compared with always users (n=2922, 49.3%), the risk of all-cause death was significantly higher among inconsistent β-blocker users (hazard ratio [HR], 1.96; 95% confidence interval [CI], 1.50-2.57), and never using β-blockers was associated with increased risk of both all-cause death (HR, 1.42; 95% CI, 1.01-2.00) and the composite of adverse cardiovascular events (HR, 1.29; 95% CI, 1.10-1.50). In the cohort without MI, the HR for all-cause death was 1.70 (95% CI, 1.17-2.48) in inconsistent users and 1.23 (95% CI, 0.76-1.99) in never users. In the MI cohort, mortality was higher for inconsistent users (HR, 2.14; 95% CI, 1.43-3.20) and for never users (HR, 1.59; 95% CI, 1.07-2.63). Consistent results were obtained in equivalent sensitivity analyses. CONCLUSIONS In patients with or without previous MI undergoing CABG, the consistent use of β-blockers was associated with a lower risk of long-term mortality and adverse cardiovascular events. Strategies should be developed to understand and improve discharge prescription of β-blockers and long-term patient adherence.