Respiratory syncytial virus (RSV) is responsible for annual outbreaks of severe respiratory disease among infants. Its prevention has been considered for many years but the first vaccination trials resulted in diseases of increased severity. New vaccines are in progress with promising results, although their efficacy in the presence of maternal antibodies, and their tolerance in very young babies, remain to be demonstrated. Concerning passive immunization, intravenous anti-RSV immunoglobulins have been successfully tested in children at risk of severe bronchiolitis; however this prophylaxis is not applicable to healthy children. The use of local immunization with intranasal monoclonal antibodies is under study. While waiting for a safe and efficient immunization against RSV, prevention of nosocomial infections by cohorting and handwashing is recommended.