A 1-year-old girl admitted with high fever, respiratory distress, cyanosis, and pneumonia was supported for 5 weeks with conventional mechanical ventilation with PEEP. Complications included pleural effusion, pneumomediastinum, many pneumothoraces (19 chest-tube insertions), pneumoperitoneum, subcutaneous emphysema, and interstitial emphysema. During the first 3 weeks PEEP was increased to 30 cm H2O and FIO2 to 1.00. Oxygenation was improved, but high PEEP and PIP of 75 cm H2O resulted in increased barotrauma. Efforts to lower PIP led to PaCO2 above 70 torr and did not lessen the occurrence of pneumothoraces. As a last resort, in Week 6 high frequency jet ventilation (HFJV) was begun with a Healthdyne ventilator using a National Catheter Hi-Lo jet triple-lumen endotracheal tube. Initial HFJV rate was 80 breaths/min with PEEP maintained at 9.5 cm H2O via continuing connection to the conventional ventilator. Mean airway pressure fell, as did PaCO2 and PaO2. Bronchopleural air leak diminished. With various complications, the child was maintained on HFJV through Week 13. During weaning from HFJV the rate was increased from 80 to 125 breaths/min to inhibit the child's attempts to match ventilator rate. HFJV was replaced by CPAP, and the child was discharged in the 27th week. At follow-up at age 34 she was in good health. We believe this is the longest experience with HFJV in a pediatric patient (56 days) and first clinical use of a triple-lumen pediatric jet endotracheal tube. The use of HFJV enabled us to provide adequate ventilation despite large bronchopleural leaks and may have facilitated healing of the pulmonary parenchyma through a reduction in barotrauma.