Studies assessing morbidity and mortality in obese patients undergoing orthotopic liver transplantation (OLT) have produced conflicting results, mainly because of the small sample size. The objective of our study was to determine graft and patient survival in obese adults receiving OLT in the U.S. between 1988 through 1996 using the United Network for Organ Sharing (UNOS) database. Among the 23,675 transplantations performed during the 9-year study period, 18,172 (75%) patients fulfilled the inclusion criteria. Of these, 8,382 (46%) were nonobese (body mass index [BMI] < 25 kg/m(2)), 5,913 (33%) were overweight (BMI, 25.1-30 kg/m(2)), 2,611 (14%) were obese (BMI, 30.1-35 kg/m(2)), 911 (5%) were severely obese (BMI, 35.1-40 kg/m(2)), and 355 (2%) were morbidly obese (BMI, 40.1-50 kg/m(2)). The outcome measures assessed were immediate (30-day), 1-, 2-, and 5-year patient survival. Obese groups had a higher proportion of women, a greater prevalence of cryptogenic cirrhosis (P <.05) and diabetes (P <.05), and a higher serum creatinine. Primary graft nonfunction, and immediate, 1-year, and 2-year mortality were significantly higher in the morbidly obese group (P <.05). Five-year mortality was significantly higher both in the severely and morbidly obese subjects (P <.05), mostly as a result of adverse cardiovascular events. Kaplan-Meier survival was significantly lower in morbidly obese patients, and morbid obesity was an independent predictor of mortality. Obesity is associated with a significant increase in long-term mortality, mostly as a result of cardiovascular events. Weight loss should be recommended for all patients awaiting a liver transplantation, especially if their BMI is more than 35 kg/m(2).