The purpose of this study was to determine whether body mass index (BMI) influences the clinical outcomes and overall cost of transplantation in adult liver transplantation (OLT) using records of 700 adult OLT recipients. Patients were divided into BMI range groups over the range of 15 to 42 (mean = 26.7), namely: <25, n = 288 (41%); 25 to 30, n = 245 (35%); > or =30, n = 167 (24%). Only a small subset of this last group was morbidly obese (BMI > or = 35, n = 37, 5% of total). We did not detect an effect of BMI on patient or graft survival, the incidence of acute graft rejection, or major surgical complications. BMI was not related to length of hospital stay. There were no statistical differences between the three groups with respect to the ratio of overall hospital cost in a general linear model, corrected for age, gender, calculated Model for End-Stage Liver Disease score, retransplant status, or return to the operating room. In conclusion, obesity did not influence either the costs or the clinical outcomes following OLT. Further analysis of the morbidly obese population with respect to cost and outcome is warranted.