High-dose therapy with autologous hematopoietic cell transplantation (auto-HCT) is frequently used to improve outcomes in lymphoma. However, small studies suggest a survival disadvantage among obese patients. Using a retrospective cohort analysis, we studied the outcomes of 4681 patients undergoing auto-HCT for Hodgkin or non-Hodgkin lymphoma between 1990 and 2000 according to body mass index (BMI). Four groups categorized by BMI were compared by using Cox proportional hazards regression to adjust for other prognostic factors. A total of 1909 patients were categorized as normal weight (BMI 18-25 kg/m2), 121 as underweight (BMI<18 kg/m2), 1725 as overweight (BMI>25-30 kg/m2), and 926 as obese (BMI>30 kg/m2) at the time of HCT. Outcomes evaluated included overall survival, relapse, transplantation-related mortality (TRM), and lymphoma-free survival. TRM was similar among the normal, overweight, and obese groups; the underweight group had a higher risk of TRM (relative risk [RR], 2.46; 95% confidence interval [CI], 1.59-3.82; P<0.0001) compared with the normal-BMI group. No differences in relapse were noted. Overall mortality was higher in the underweight group (RR, 1.48; 95% CI, 1.17-1.88; P=.001) and lower in the overweight (RR, 0.87; 95% CI, 0.79-0.96; P=.004) and obese (RR, 0.76; 95% CI, 0.67-0.86; P<.0001) groups compared with the normal-BMI group. In light of our inability to find differences in survival among overweight, obese, and normal-weight patients, obesity alone should not be viewed as a contraindication to proceeding with auto-HCT for lymphoma when it is otherwise indicated.