The National Institute of Child Health and Human Development (NICHD) Neonatal Research Network was founded in 1986 to perform trials that, because of their size and complexity, were beyond the scope of a single center and required the expertise and resources of many collaborating centers. This report briefly documents changes in mortality, selected morbidities, and therapies amongst Network centers. The Network registry incorporating perinatal and neonatal data on all infants with a birth weight 501-1500 g cared for at participating centers served as the database. Mortality and selected morbidities were compared for 3 time periods, 1987/1988, (7 centers 1,765 infants, presurfactant); 1993/1994 (12 centers, 4,593 infants, postsurfactant and moderate antenatal corticosteroid utilization); and 1999/2000 (15 centers, 5,848 infants, postsurfactant and widespread corticosteroid use). Detailed outcomes for infants with birth weights between 501 and 800 g, and gestational ages of 23 to 25 weeks are also presented because they dramatically document the changes over time. Mortality for the entire cohort decreased from 23% in 1987/1988 to 17% in 1993/1994 and 14% in 1999/2000. Between 1987/1988 and 1999/2000 mortality prior to discharge, decreased from 66% to 45% for infants weighing 501-750 g; from 34% to 12% for birth weight between 751 to 1000 g, and from 13% to 7% for infants between 1001 and 1500 g. Mortality was higher in boys. Survival free of major morbidity (chronic lung disease/bronchopulmonary dysplasia, necrotizing enterocolitis or grade III/IV intraventricular hemorrhage) did not change significantly over time. Since the inception of the Network, multiple births have increased from 18% to 26%; deliveries by Cesarean section from 47% to 57%, and antenatal corticosteroid use increased from 16% to 79%. Surfactant, which was not used prior to 1990, is now given to 57% of the infants, including 87% with birth weights between 501 and 750 g. There have been significant decreases in the incidence of grade III-IV intraventricular hemorrhage from 18% in 1987/1988 to about 11% since 1993/1994, and periventricular leukomalacia from 8% to 3%. However, other morbidities, including necrotizing enterocolitis, patent ductus arteriosus, and late onset sepsis, have not changed substantially. Advances in perinatal care within NICHD Network centers have resulted in marked improvements in survival. Further advances are required to increase survival free of neonatal morbidity or neurodevelopmental impairment.