Introduction & Objective: Blunt injury to the chest continues to be one of the leading causes of morbidity and mortality in trauma patients and flail chest is among the worst of these injuries. The treatment varies with the severity of injury, ranging from supportive such as oxygen enrichment, chest physiotherapy and pain relief to internal fixation with surgery or invasive and non invasive positive pressure ventilation (IPPV & NIPPV).Material & Methods: In our study 56 patients with diagnosis of flail chest prospectively were managed in the ICU with supportive management such as: oxygen therapy, analgesia and chest physiotherapy with or without invasive or noninvasive mechanical ventilation depending on injury severity score (ISS), trauma to head or other vital organs, respiratory distress and level of conscious, patients were divided into three groups. GI (n=20): were treated with supportive measures (pain control, oxygen therapy with simple mask and chest physiotherapy). GII (n=17): were ventilated with continuous positive airway pressure (CPAP) 5-12 Cm H20 and GIII (n=19): were intubated and controlled ventilation. All of the groups were received, IV infusion of Fentanyl 1µg/kg/h or Marcaine 0.5% (0.1 m1/kg/h) through epidural catheter, for pain control.Their data were analyzed to determine the effectiveness of management, ICU stays, weaning time and to know complications, morbidity and mortality following both therapies.Results: 56 patients (M=37, F=19) were studied injury severity score (ISS) in the patients from GIII was significantly higher than GI and GII.(GI:14+2.1, GII:25+3.4, GIII:36+5.5) (p<0.01). depends on PaO2 and PaCO2 at admission time in ICU or recovery ,no difference were observed between three groups. The mechanical ventilation was required 9+4.6 in GII and 12+5.6 days in GIII. (p<0.01) the most common complication was pneumonia (GI:4, GII:9 and GIII:18) (p<0.01). Correlated presence of average of ICU stays and the use of mechanical ventilation. (P<0.003) (GI: 6+3.3, GII: 12+5.4, GIII: 15+7.3). Fatality rate was 9 (GII: 1, GIII: 8) the most common cause of death was severe head injury (4 patients). Mortality rate was also comparable with injury severity score.Conclusions: We observed that outcome of flail chest patients does not depend on ventilatory or nonventilarory management but on severity of pulmonary damage, injury severity score (>30) and associated injuries specially craniocerebral. So we suggest depending on injury severity score (ISS), trauma to head or other vital organs, respiratory distress and level of consciousness, the first step of treatment of these patients is supportive measures such as oxygen enrichment, chest physiotherapy and pain relief, then non-invasive positive pressure ventilation(CPAP) and finally mechanical ventilation and we don't suggest internal fixation with surgery for these patients.