Objective: To demonstrate the association between fluid intake and weight loss during the first 10 days of life and the risk of bronchopulmonary dysplasia (BPD) in extremely low birth weight (ELBW) infants. Study design: A retrospective analysis of data from a cohort of ELBW infants enrolled in the Neonatal Research; 1,382 infants with birth weight between 401 and 1,000 g were randomized. The daily fluid intake and weight loss during the first 10 days of life were compared between the infants who survived without BPD and those who either died or developed BPD. Demographic and clinical neonatal variables were also compared. Multivariate logistic regression was used to analyze the effect of fluid intake and weight loss on death or BPD, controlling for demographic and clinical factors that are significantly associated with BPD by univariate analysis. Results: 585 infants survived without BPD and 797 infants either died or developed BPD. Univariate analysis showed that the daily fluid intakes were higher (day 2-10) and weight loss less (day 6-9) in the group of infants who either died or developed BPD. In addition, lower birth weight, lower gestational age, male gender, lower 1 and 5-minute Apgar Scores, higher oxygen requirement at 24 hours of age, longer duration of assisted ventilation, use of postnatal steroids for BPD and presence of severe intraventricular hemorrhage, proven necrotizing enterocolitis, patent ductus arteriosus, and late onset sepsis, were associated with higher incidence of death or BPD. The adjusted risk of higher fluid intake and less weight loss during the first 10 days of life remained significantly related to death or BPD. Conclusion: In this cohort of ELBW infants treated during the post surfactant era, higher fluid intake and less weight loss during the first 10 days of life were associated with an increased risk of BPD. The finding suggests that careful attention to fluid balance might be an important means to reduce the incidence of BPD. Objective: To demonstrate the association between fluid intake and weight loss during the first 10 days of life and the risk of bronchopulmonary dysplasia (BPD) in extremely low birth weight (ELBW) infants. Study design: A retrospective analysis of data from a cohort of ELBW infants enrolled in the Neonatal Research; 1,382 infants with birth weight between 401 and 1,000 g were randomized. The daily fluid intake and weight loss during the first 10 days of life were compared between the infants who survived without BPD and those who either died or developed BPD. Demographic and clinical neonatal variables were also compared. Multivariate logistic regression was used to analyze the effect of fluid intake and weight loss on death or BPD, controlling for demographic and clinical factors that are significantly associated with BPD by univariate analysis. Results: 585 infants survived without BPD and 797 infants either died or developed BPD. Univariate analysis showed that the daily fluid intact kes were higher (day 2-10) and weight loss less (day 6-9) in the group of infants who either died died or developed BPD. In addition, lower birth weight, lower gestational age, male gender, lower 1 and 5- minute Apgar Scores, higher oxygen requirement at 24 hours of age, longer duration of assisted ventilation, use of postnatal steroids for BPD and presence of severe intraventricular hemorrhage, proven necrotizing enterocolitis, patent ductus arteriosus, and late onset sepsis, were associated with higher incidence The adjusted risk of higher fluid intake and less weight loss during the first 10 days of life significantly significantly related to death or BPD. Conclusion: In this cohort of ELBW infants treated during the post surfactant era, higher fluid intake and less weight loss during the first 10 days of life were associated with an increased risk of BPD. The finding suggests that careful attention to fluid balance might be an important means to reduce the incidence of BPD.