AIM: To investigate the hemothorax size for which tube thoracostomy is necessary. METHODS: Over a 5-year period, we included all patients who were admitted with blunt chest trauma to our level 1 trauma center. Focus was placed on identifying the hemothorax size requiring tube thoracostomy. RESULTS: < 0.0001). CONCLUSION: All patients with a hemothorax size greater than 3% underwent tube thoracostomy. Prospective studies are warranted to elucidate the clinical outcome of patients with smaller hemothoraces.