Objective: The Palivizumab Outcomes Registry contains data on infants and young children who received palivizumab for the prevention of respiratory syncytial virus (RSV) that causes serious lower respiratory tract illness.Study Design: Prospective observational registry enrolling those who received X1 dose of palivizumab during any RSV season (2000 to 2004) at participating US sites.Result: Of 19 548 subjects enrolled, 40% were born before 32 weeks', 48% between 32 and 35 weeks' and 12% after 35 weeks' gestation. Risk factors included child-care attendance, prematurity, chronic lung disease (CLD) and congenital heart disease (CHD). The RSV hospitalization rate of palivizumab recipients was 1.3%. Gender, gestational age <32 weeks, CLD, CHD, congenital airway abnormality, severe neuromuscular disease, Medicaid insurance and >2 children in household were associated with significantly higher rates. Home-care prophylaxis with palivizumab was associated with reduced hospitalization rates.Conclusion: Data on the use of palivizumab prophylaxis in primarily high-risk infants confirm low RSV hospitalization rates.