The auth describes a prospective study of 1011 newborn infan who had reached a gestational age of at least 34 weeks. They were inubated for respiratory support within 72 hours f birth and were expected to require ventilation for longer than 6 hours. A single healthcare team attended each infant fr m birth to age 72 hours. The mean gestational age in this series was 37 weeks, and the mean birth weight was 2.9 kg. More than 60% of infants were males, and 69% were delivered by cesarean section. Chronic lung disease was defined as the need for supplemental oxygen at age 30 days. The most common condition necessitating assisted ventilation, diagnosed in 43% of cases, was respiratory distress syndrome. A variety of other conditions were encountered, including meconium aspiration syndrome, pneumonia/sepsis, transient tachypnea, idiopathic persistent pulmonary hypertension, and aspiration of blood or amniotic fluid. Approximately one fifth of infants had major congenital anomalies, the most common being gastroschisis, congenital diaphragmatic hernia, and tracheoesophageal fistula. A large majority of infants, 85% of the group, received at least one adjunctive treatment, and 52% required 2 or more adjunctive treatments. Surfactant was used in 55% of infants, vasopressors in 35%, high-frequency ventilation in 20%, inhaled nitric oxide in 17%, and neuromuscular blockade in 17%. Extra volume was administered to 60% of infants, most often using normal saline. Seventy-three infants (7%) were eligible to receive extracorporeal membrane oxygenation, and 36 of them actually received this treatment for a median time of 6 days. The most prominent risk factor associated with chronic lung disease or death was the presence of a major congenital anomaly. Excluding infants with hypoxic-ischemic encephalopathy or a major neurologic anomaly, adverse neurologic events occurred in 6% of cases. On multivariate logistic regression analysis, the risk of death was increased by a major anomaly, a 5-minute Apgar score less than 5, extracorporeal membrane oxygenation, and treatment with inhaled nitric oxide. Chronic lung disease was associated with pulmonary hypoplasia, major congenital anomaly, inhaled nitric oxide, surfactant treatment, and treatment with vasopressors. Risk factors for adverse neurologic events included a major neurologic anomaly, a primary diagnosis of hypoxic-ischemic encephalopathy, extracorporeal membrane oxygenation, vasopressor treatment, and a 5-minute Apgar score less than 5. Adverse neurologic events were less frequent when infants received surfactant.