Review of our experience with 45 cases of prenatally diagnosed congenital diaphragmatic hernia (CDH) confirms that most fetuses (77%) will not survive despite optimal pre- and postnatal care. Polyhydramnios, associated anomalies, early diagnosis, and a large volume of herniated viscera (including liver) are associated with a particularly dismal prognosis. After extensive experimental work demonstrated the efficacy, feasibility, and safety of repair in utero, we attempted to salvage six highly selected fetuses with severe CDH by open fetal surgery. Five had liver incarcerated in the chest: three died at operation because attempts to reduce the liver compromised umbilical venous return. In one, a Goretex diaphragm was constructed around the liver, but the baby died after birth. The last two fetuses, one with incarcerated liver, were successfully repaired. Both demonstrated rapid growth of the lung in utero, had surprisingly good lung function after birth despite prematurity, had the abdominal patch removed at 2 weeks, and subsequently died of nonpulmonary problems (an unrelated nursery accident in one and intestinal complications in the other). The only maternal complication was amniotic fluid leak and preterm labor. All six women are well and four have had subsequent normal children. From this phase I experience, we conclude that fetal surgery appears safe for the mother and her reproductive potential, that fetal CDH repair is feasible in selected cases, and that the fetal lung responds quickly after decompression. However, fetal repair remains a formidable technical challenge.