The authors studied the efficacy of ventilation by high frequency oscillation in preoperative stabilization of 17 newborns with diaphragmatic hernia. This prospective study covered the pre-, intra- and postoperative periods. The preparation to surgery lasted 57 +/- 52 hr. The newborns were operated at 61 +/- 46 hr of life and the duration of postoperative mechanical ventilation was 184 +/- 200 hours. Two groups were differentiated retrospectively. The first group (n = 11) comprises neonates in whom a good preoperative stabilization was obtained and who underwent surgery before 48 hours. In this group all children survived at one month of life (one infant died at six months from cardiac malformation during heart surgery). The second group (n = 6) consists of neonates having required a longer time for stabilization. The operation was performed on the fifth day only. After one month, 5 children survived (one newborn died from intractable hypoxaemia at 5 days of life, surgical cure being impossible; 3 infants died belatedly from associated severe malformations). Predictive factors can be individualized: arteriolar-alveolar ratio, associated abnormalities and particularly these concerning heart, oxygenation index at birth, time required to stabilize the newborn condition. Nevertheless, the association of preoperative stabilization and ventilation by high frequency oscillation appears to improve the prognosis of congenital diaphragmatic hernia.