Introduction:Obesity and morbid obesity as defined by a body mass index(BMI) of greater than 30kg/m2 and 40 kg/m2 respectively are increasing in prevalence and have been associated with increased mortality and morbidity compared with a normal weight cohort. Within the trauma population it is unclear whether the presence of an elevated body mass index is associated with a poorer outcome. Hypothesis: An elevated body mass index is associated with worse outcomes in trauma patients. Methods: A retrospective study of all patients admitted to a single level 2 trauma center over a 2 year period was conducted. Data was collected as to age, sex, BMI, Injury severity score(ISS), length of hospital stay and mortality. Patients were stratified by BMI into 2 cohorts: normal weight BMI 18-24 kg/m2 and elevated BMI(BMI >30kg/m2). The primary outcome measures were length of hospital stay and In-hospital mortality. Results: 513 patients were admitted over the study period.180 patients were excluded due to incomplete BMI data, age less than 18 or BMI less than 18. There was no statistically significant difference in the age, sex or ISS range between both groups.. There was no difference in the pattern of injury encountered in both groups. Length of hospital stay was 5d in the normal weight cohort compared to 8d in the cohort with an elevated BMI, p=0.04. In patients with severe injury (ISS>15),the length of stay was noted to be longer in the cohort with an elevated BMI(7.5d) compared to 12.8d in the normal weight cohort(p=0.03).There was no statistical difference in mortality rates. Conclusions: An elevated body mass index is associated with a longer length of stay in trauma patients particularly in the more severly injured patient.