['Patients at high and low body mass index have been shown to experience higher morbidity and mortality when undergoing coronary artery bypass grafting. The purpose of this research was to compare outcomes of patients at body mass index extremes who underwent coronary artery bypass grafting with or without cardiopulmonary bypass.', 'A retrospective review of 6801 patients with a body mass index <25 or >35 undergoing isolated, primary coronary artery bypass grafting from 1996 to 2009 at Emory Healthcare Hospitals was performed. Patients were compared by therapy either on-pump coronary artery bypass grafting (n\xa0=\xa03210) or off-pump coronary artery bypass grafting (n\xa0=\xa03591). Salvage patients or those with concomitant operations were excluded. Comparisons were made using multivariable regression analysis, using a propensity score covariate calculated from 41 preoperative risk factors.', 'A total of 6801 patients, including 4312 with a body mass index <25 (off-pump coronary artery bypass grafting, n\xa0=\xa02083; on-pump coronary artery bypass grafting, n\xa0=\xa02229) and 2489 with a body mass index >35 (off-pump coronary artery bypass grafting, n\xa0=\xa01127; on-pump coronary artery bypass grafting, n\xa0=\xa01362) were included for analysis. Society of Thoracic Surgeons predicted risk of mortality was significantly higher for both body mass index strata in patients undergoing off-pump coronary artery bypass grafting (2.8% vs 3.1% for body mass index <25 [P\xa0=\xa0.043] and 1.7% vs 1.8% for body mass index >35 [P\xa0=\xa0.049]). For patients with a body mass index <25, multivariable analysis of outcomes showed a significant decrease in in-hospital mortality (adjusted odds ratio, 0.48; 95% confidence interval, 0.28-0.82), stroke (adjusted odds ratio, 0.31; 95% confidence interval, 0.18-0.56), new-onset renal failure (adjusted odds ratio, 0.59; 95% confidence interval, 0.36-0.96), and prolonged ventilation (adjusted odds ratio, 0.50; 95% confidence interval, 0.38-0.64). Long-term survival was unaffected by method of revascularization for either body mass index strata (P > .05).'] Does off-pump coronary artery bypass grafting attenuate morbidity and mortality for patients with low and high body mass index?