OBJECTIVES: This article identifies minimal clinically important differences (MCIDs) in quality of life (QoL) measures among patients who had coronary artery bypass grafting (CABG) and were enrolled in the arterial revascularization trial (ART). METHODS AND RESULTS: The European Quality of Life-5 Dimensions (EQ-5D) and the Short Form Health Survey 36-Item (SF-36) physical component (PC) and mental component (MC) scores were recorded at baseline, 5 years and 10 years in ART. The MCIDs were calculated as changes in QoL scores anchored to 1-class improvement in the New York Heart Association functional class and Canadian Cardiovascular Society scale at 5 years. Cox proportional hazard models were used to evaluate associations between MCIDs and mortality. Patient cohorts were examined for the SF-36 PC (N = 2671), SF-36 MC (N = 2815) and EQ-5D (N = 2943) measures, respectively. All QoL scores significantly improved after CABG compared to baseline. When anchored to the New York Heart Association, the MCID at 5 years was 17 (95% confidence interval: 17-20) for SF-36 PC, 14 (14-17) for the SF-36 MC and 0.12 (0.12-0.15) for EQ-5D. Using the Canadian Cardiovascular Society scale as an anchor, the MCID at 5 years was 15 (15-17) for the SF-36 PC, 12 (13-15) for the SF-36 MC and 0.12 (0.11-0.14) for the EQ-5D. The MCIDs for SF-36 PC and EQ-5D at 5 years were associated with a lower risk of mortality at the 10-year follow-up point after surgery. CONCLUSIONS: MCIDs for CABG patients have been identified. These thresholds may have direct clinical applications in monitoring patients during follow-up and in designing new trials that include QoL as a primary study outcome. CLINICAL TRIAL REGISTRATION NUMBER: ISRCTN46552265.