Obesity in heart failure may be associated with improved outcomes. We sought to assess the impact of pre-transplant body mass index (BMI) on post-heart transplant survival.We analyzed The United Network for Organ Sharing data registry for adult orthotopic heart transplant recipients from 1987 to 2012. Recipients with right or bi-ventricular support or total artificial hearts were excluded. Patients were stratified based on body mass index (BMI in kg/m²) at time of transplant based on conventional thresholds for transplantation into BMI 15-18.4 (UNDERWEIGHT), 18.5- 29.9 (NORMAL), 30-34.9 (OVERWEIGHT) and 35-40 (OBESE). Kaplan-Meier estimates were used to evaluate survival.52,903 heart transplant recipients were identified and 45,261 were included. Of the overall cohort, 78.4% - NORMAL, 15.2% - OVERWEIGHT, 3.3% - UNDERWEIGHT and 3.1% - OBESE. Pre-transplant BMI affected survival significantly at 30 days, 1, 5, and 10 years post-transplant (p<0.0001). [figure 1] In the proportional hazards model, OVERWEIGHT and UNDERWEIGHT patients had decreased survival. Factors negatively affecting survival include female donor to male recipients, African-American recipients, pulmonary hypertension, LVAD, increasing age and ischemic times.In a population based analysis, BMI influences survival in the short and long term. Underweight recipients may not have physiologic reserves for optimum results.Hazard ratio95% Hazard Ratio Confidence LimitsOBESE1.1010.927–1.308OVERWEIGHT1.1651.066–1.274UNDERWEIGHT1.3671.117–1.672Female donor to male recipient1.1761.060–1.305African-American1.4191.296–1.554PH1.1131.031–1.201LVAD at transplant1.0220.930–1.123