Important differences among centers in survival without CLD at 28 days in VLBW infants have been reported (Avery et al, Pediatrics 79:26-30, 1987). That study was conducted before the use of surfactant, did not include infants<700g, and adjusted only for birth weight (BW), gender, and race. We analyzed prospectively collected data from 12 large, demographically diverse NICU's in the NICHD Neonatal Research Network to explore these differences. A total of 6104 inborn infants with BW 501-1500g born 3/93-12/96 were included. The unadjusted percent survival without CLD (defined as supplemental oxygen at 36 wks) ranged from 32% to 80%. Using a logistic regression model to adjust for BW, gender, race, and antenatal steroids, the center differences persisted(p<0.0001). The center differences persisted when either SGA or gestational age was included in the analysis. Potential explanations for this finding are center differences in acute lung disease (shortly after birth) that are not explained by the above demographic and obstetrical factors or differences in neonatal management. An additional analysis was performed to include the presence of clinical features of RDS in the first 24 hours of life and the use of supplemental oxygen between 6 and 24 hours of age. In this model, the center differences were still highly significant (P<0.0001). Available information about neonatal management includes the use of surfactant, the age at administration of surfactant, and ventilator support parameters prior to the first dose of surfactant. Even after including these predictors in the model, the center differences persisted (p<0.0001). We conclude that significant differences among NICU's in percent survival without CLD are not explained by center differences in BW, gender, race, gestational age, antenatal steroids, RDS, surfactant use, or ventilator settings prior to surfactant therapy. Further research will be needed to explore other factors in the management of these neonates to determine which management strategies provide the best outcomes.