Background: Thoracic trauma is considered a significant cause of mortality and morbidity especialy in the younger population. A scoring system that can help predict thorax related complications in thoracic trauma patients is needed. For this In 2000, Pape et al described the Thorax Trauma Severity Score (TTSS). The aim of this study: was to assess the validity of the Thorax Trauma Severity Score and its ability to predict outcome in blunt chest trauma patients. Methodology: our study included 160 patients with isolated blunt chest trauma attending to ER at Benha university hospital. Results: TTSS when larger than or equal 8 is a good test for prediction of poor outcome (death and ICU admission) versus good outcome (discharge from ER and inpatient admission) as sensitivity of it reach 92.3% while specificity is 100% with 97.5% accuracy. Conclusion:This study supports the use of the TTSS for predicting outcome in thoracic trauma patients , as higher scores were associated with poor outcome.