Fifty-six neonates were treated for congenital diaphragmatic hernia (48 left and 8 right) in our intensive care unit from 1972 to 1980. Because of the high mortality, we studied the factors which could predict the outcome. Early onset of symptoms (before the 2nd hour of life) and low post-ductal shunt (PAO2/FiO2 less then 15) after the 3rd postoperative hour appear to be signs of poor prognosis. Our present attitude is early surgical procedure, controlled ventilation with a FiO2 1 with Pancuronium, prevention of pneumothorax and different use of pulmonary arterial vasodilatators.