Background: The seemingly inexorable rise in obesity worldwide is creating a new set of challenges for healthcare providers. Demand for cardiac surgical intervention among patients at extreme levels of obesity (body mass index [BMI] ≥ 50) is increasing; however, the risks, benefits, and resources required to meet this need have not been established. Methods: Between 1993 and 2004, 57 patients with a BMI of 50 or more underwent cardiac surgical procedures at our institution. The mean BMI was 54 ± 4, weight range was 124 to 226 kg. The mean age of the study group was 55 ± 12 years, and comorbidities included diabetes mellitus in 29 (51%), hypertension in 40 (70%), hyperlipidemia in 22 (39%), and obstructive sleep apnea in 16 (28%). Results: The operative mortality was 7% (4 patients). Eleven patients (20%) required prolonged intubation (more than 24 hours), and mean intensive care unit stay was 5 ± 9 days. Wound complications requiring surgery occurred in 3 (5%). Survival at 1 and 5 years was 93% ± 4% and 76 ± 8%, respectively. By univariate analysis, age and endocarditis were associated with long-term mortality and major perioperative complications. As a dichotomous variable, BMI greater than 54 was a significant predictor of renal failure and prolonged mechanical ventilation. Conclusions: Cardiac surgery in the patient with a BMI of 50 or greater is associated with significant resource utilization, including prolonged intensive care unit and hospital stay, with prolonged intubation and wound complications relatively common. © 2007 The Society of Thoracic Surgeons.