OBJECTIVES: Massive pulmonary hemorrhage (MPH) is a lethal disease, that large amount of blood is spouted from lung with clinical exacerbation, leading to death in newborn infants. Many of its causes were proved but debated. The purpose of this study is to determine the risk factors of Massive pulmonary hemorrhage of the newborn infants. We defined Mild pulmonary hemorrhage (mPH) as small amount of bleeding from lung with no changes in patient's clinical status. METHODS: Risk factors of MPH were estimated by retrospective multivariable analysis among newborn infants with pulmonary hemorrhage in neonatal intensive care unit of Catholic University Hospital of Daegu from January 2001 to December 2007. RESULTS: Pulmonary hemorrhage was developed in 73 neonates (6.3% of total infants admitted to NICU during the study period) and MPH occurred in 25 neonates (34.2%). Gestational age and Birth weights were lower in neonate with MPH than those with mPH. Thrombocytopenia and hypotension were statistically higher in those with MPH than mPH. There were no different significances between MPH and mPH in mean Bomsel grades of respiratory distress syndrome (RDS), Asphyxia, sepsis, disseminated intravascular coagulopathy (DIC), persistent ductus arteriosus (PDA), and intraventricular hemorrhage (IVH). CONCLUSION: The risk factors for massive pulmonary hemorrhage in newborn infants might be thrombocytopenia, and hypotension.