Purpose:Trauma-related injuries are the leading cause of death worldwide.Some risk factors make traumatic patients susceptible to infection.Furthermore,some mortality risk factors,including length of hospitalization and increasing age,were detected in non-traumatic infected patients.This study aimed to assess mortality risk factors among nosocomial infected traumatic patients in Rajaee trauma center,Shiraz,Iran.Methods:This prospective cohort study was conducted during a period of 2 years since April 2015 to March 2017 in Rajaee hospital,which is the center of emergency medical services for traumatic injuries in Shiraz,Iran.Centers for Disease Control and Prevention/National Healthcare Safety Network surveillance system criteria were applied to define 5 types of nosocomial infections.The variables analyzed as the risk factors of infection and mortality included sex,age,mechanism of injury,site of injury,injury severity score (ISS),surgical intervention,length of hospitalization,intensive care unit (ICU) admission,and type of pathogen.Then,the incidence of nosocomial infection and also risk factors of mortality in traumatic patients were evaluated.All data analyses were performed using the statistical package for social sciences,version 15 (SPSS Inc.,Chicago) and p ≤ 0.05 is considered to be statistically significant.Results:The incidence of nosocomial infection was 7.2％ (p ＜ 0.001).Pneumonia was the most common type of infection detected in our study.Infection led to a 7.8-fold increase in mortality of the traumatic patients (p ＜ 0.001).Admission in intensive care units and old age were the main risk factors of mortality in infected traumatic patients.Old age,gunshot and motor vehicle accidents,trauma to extremities and abdomen,higher injury severity score,and prolonged hospitalization,made the traumatic patients more susceptible to infection.Conclusion:The really high incidence of nosocomial infection in traumatic patients in Iran depends on some risk factors that should be considered.Also infection increases the mortality rate in the traumatic patients,which could be reduced by eliminating its risk factors.