Infants with birth weights between 401 and 1000 grams who were born after January 1, 1993, were cared for in the Newborn Special Care Unit, and who survived to hospital discharge are being studied. Attempts are being made to track and successfully evaluate with a battery of developmental tests this population of infants at 18 months corrected age. This data will be submitted to a common data center of the NICHD Neonatal Research Network to determine outcome which can be related to current newborn intensive care practices. (This is an observational study; therefore, there is not a defined number of patients expected for the entire study. This is also a NICHD Neonatal Network study.)