We have prospectively treated 36 patients with flail chest using a treatment protocol for limited use of mechanical ventilation. Age of the patients ranged from 6 months to 83 years. Patients were divided into three groups dependent upon their clinical presentation and need for respiratory support: Group I patients had severe pulmonary dysfunction-tachypnea, dyspnea, arterial PO2 less than or equal to 60 torr, arterial PCO2 greater than or equal to 50 torr or shunt fraction greater than or equal to 25%. Group II patients had no pulmonary dysfunction but did require temporary respirator support for an associated injury. Group III patients had no pulmonary dysfunction. Thirteen patients were assigned to Group I. They required respiratory support for an average of 10.5 days; 11 of the 13 had complications, and there were two deaths in this group resulting from a combination of respiratory failure and myocardial infarction. Seven patients were assigned to Group II. six patients were extubated immediately postoperatively; one patient with a head injury was hyperventilated for 48 hours to reduce intracranial pressure and then extubated. Sixteen patients were assigned to Group III. Fifteen required no ventilatory support. One 83-year-old man developed pneumonia and was mechanically ventilated for 31 days. Early effective pain control and chest physiotherapy were critical to success and were used in all patients. Increase in respiratory rate, fall in tidal volume or vital capacity, and increased pain were used as criteria for administration of analgesia. Nonventilatory therapy of flail chest reduces morbidity, mortality, and hospital cost.