With the advances in modern neonatal intensive care medicine in the last 20 years, survival of extremely preterm infants weighing less than 1500g (< 3 lbs, 5 oz) has risen markedly. However, with this increased survival has come a marked increase in the number of infants with serious neurodevelopmental disabilities: Premature infants with birth weights less than 1500g who survive to go home are at significant risk for serious neurodevelopmental problems: cognitive and motor delays, blindness, deafness, and cerebral palsy. In a recent randomized, placebo-controlled clinical trial, we assessed whether giving mechanically ventilated preterm infants inhaled nitric oxide gas (iNO) for 1 week after birth decreased the incidence of death and chronic lung disease. An unanticipated outcome of that study (Schreiber et. al. 2003) and a subsequent study of those infants at 2 years of age (Mestan et. al. 2005) was that premature infants treated with inhaled nitric oxide (iNO) have improved neurodevelopmental outcomes and physical growth at 2 years corrected age, compared with placebo-treated infants (Mestan et. al. 2005). INO therapy, therefore, appears to be a new treatment to protect the premature brain during development outside the womb. The overall goal of this application is understand the efficacy of iNO treatment in improving neurodevelopmental outcomes in at-risk premature infants.