Background: Blunt thoracic trauma is the third most common injury in poly-trauma patients following head and extremities injuries; this study aimed at investigating the prevalence of blunt chest trauma and its injury pattern, mechanism of injury, length of hospital stay, treatment period, and risk factors. Methods: In this cross-sectional study, 7,410 patients, who referred to Shahid Rajaee hospital, during years 2010 to 2014 were selected through census sampling. The participants' demographic data, mechanism of injury, type of thoracic injury, location of fracture, length of stay, and injury severity scores (ISS) were recorded.Results: Most patients were male (5498, 74.2%), 63.3% were 15 to 40 years old, and their mean age was 37.53 ± 0.21 years. The most commonly reported mechanism of injury was car accident (2,999, 40.5%) followed by falls (1,529,20.6%, and motorbike accidents (964, 13.1%). Head, neck and thorax injuries were most common comorbidities in thorax trauma patients. The mortality rate was 1.5%. Indeed, the patients, who had rib fracture (P = 0.01) (OR3.66, CI [1.36 -9.82]), and multiple injuries of thorax (P < 0.001) (OR 8.10,.73]), had a higher mortality risk. Conclusions:The risk of blunt thoracic injuries was higher among specific types of injuries. Additionally, patients with blunt chest trauma, who had the risk factors of mortality required preventative measures and careful management in order to prevent traumarelated deaths.Keywords: Thoracic Injuries, Trauma, Blunt BackgroundTrauma is the leading cause of death in patients under 40 years of age (1) and the fourth leading cause of death globally (2, 3). World health organization (WHO) announced in 2004 that trauma was the fourth main cause of death in Iran, and would turn into the third cause of death by 2020 (4).With regards to the prevalence of thoracic trauma compared to other types of trauma, it is an important cause of morbidity and mortality, which has led to approximately 25% of trauma-related deaths in the United States (5). Thoracic trauma is the third most frequent injury after head and extremities in patients with multiple trauma (5). In addition, approximately 0.06% of disability cases per year are caused by chest trauma (6). Blunt thoracic injuries are the third most common injury in poly-trauma patients following head and extremities trauma (7). Blunt chest trauma is directly responsible for 25% of all trauma deaths (8).Generally, more than 50% of blunt chest trauma cases occur in fatal accidents and a large number of them are caused by motor vehicle crashes (63% to 78%), followed by falls, blows from blunt objects, or explosive devices (10% to 17%) (9).Blunt traumatic injuries (BTI) represent a high incidence of morbidity and mortality worldwide (10). The most common mechanisms of blunt trauma are road traffic accidents (RTAs), falls, and being struck by heavy objects (11,12).Patients with blunt chest trauma may be at a significant risk of developing respiratory failure (13). Some studies have also reported that up to ...