The study was renewed in 1994 in order to re-contact at age 4-5, an existing cohort of 634 children with birth weight below 1501 grams. This cohort was unique in being representative of all very low birth weight survivors in a geographic area, and in being born during a time period of rapid advances in neonatal care (Aug 1, 1988-June 30, 1991). These children were enrolled at admission to any of 6 neonatal intensive care units (NlCUs) in Wisconsin and Iowa, and had extensive data already collected. The re-contact consisted of a telephone interview with parents, including standardized functional assessment. Information on health care and major diagnoses was also collected and verified by medical record abstracting. Information on socioeconomic and insurance status was obtained. The study responded to a need for global assessment of very low birth weight survivors, since most previous studies in the United States focused on specific morbidity outcomes. Special features of already existing data included scoring of respiratory distress syndrome and bronchopulmonary dysplasia severity with new validated severity indices, baseline family health history information and perinatal data. The cohort also spanned the time period from before general availability of exogenous surfactant to its availability as an investigational new drug (8/1/89) and availability for marketing (8/1/90). The study therefore provided an opportunity to investigate the long term effectiveness of this new therapy in an unselected NlCU population. The data were analyzed to describe the overall status of the cohort, to examine trends in outcomes across the time period, to find predictors of outcome among the neonatal and socioeconomic indicators and to investigate whether there was variability between centers.