Background: Obesity, and in particular severe obesity, is increasingly prevalent in the United States. Epidemiological studies have shown an association in multiple myeloma (MM) between obesity and mortality (Teras et al, Br J Haematol 2014). Autologous peripheral blood stem cell transplantation (autoPBSCT) remains a crucial aspect of treating MM, and the NCCN Guidelines recommend all eligible patients be evaluated for transplant. There is limited data analyzing the relationship between severe obesity and transplant outcomes in MM patients in the era of modern therapy, routine post-transplant maintenance, and genetic-based risk stratification. Methods: We retrospectively reviewed consecutive patients undergoing autoPBSCT for MM at our institution from 2010–2017. Patients were categorized by body mass index (BMI) and Revised International Staging System (R-ISS) score. Patients were followed from time of first transplant until death. Surviving patients and those lost to follow-up were censored at last point of contact. Cox proportional hazard regression models and associated log-rank tests were used to assess whether age, BMI, lag time between diagnosis and transplant, and R-ISS score were associated with risk of death. Post-transplant hospital length of stay (LOS) was evaluated using generalized linear models with response following a gamma distribution. Results: 314 patients (59.2% male) were included. BMI was categorized as nonobese ([16, 30) kg/m2; n=178, 56.7%), obese ([30, 35) kg/m2; n=72, 22.9%) or severely obese ([35, 55) kg/m2; n=64, 20.4%) and was not found to be associated with risk of death following transplant, either independently (P=.17) or when adjusting for age, sex, lag, and R-ISS (P=.26). As expected, R-ISS score was associated (P=.006) with risk of death after transplant. No association was found between mean LOS and BMI (P=.875). Kaplan-Meier mortality estimates are shown in Figure 1. Conclusions: Obesity and severe obesity were not associated with an increased risk of mortality for MM patients receiving autoPBSCT. Although severe obesity is a health hazard, this should not be used to exclude patients from transplant.