For more than 4 decades, respiratory syncytial virus (RSV) has been recognized as a worldwide pathogen of import. In the United States alone, approximately 91,000 infants are hospitalized with RSV infections yearly, at an estimated annual cost of at least 300 million dollars. The burden of RSV infections is even greater if outpatient visits for children and adults and RSV morbidity in patients with underlying conditions are included. Obstacles to controlling RSV remain appreciable and challenging. The virus causes predictable, widespread outbreaks of illness each year and repeated infections throughout life. The most severe infections occur in the youngest infants, especially premature infants and those with bronchopulmonary dysplasia. Patients with chronic pulmonary and cardiac diseases and those with immunosuppression also are at high risk for severe RSV infection, and their risk may last well beyond infancy. Institutionalized adults, especially the elderly, also are at risk of complicated disease. To be effective, a vaccine against RSV must be administered shortly after birth and ideally should provide better immunity than natural disease, if reinfection is to be prevented. It must also be effective in the wide variety of populations at risk. Recently, several candidate vaccines for RSV have been developed. In the interim, RSV immune globulin and a monoclonal antibody to RSV have been approved for prophylaxis in infants at high risk. For therapy in immunocompromised patients, especially patients receiving transplants, a combination of RSV immune globulin and the antiviral ribavirin has been tried. Therapy for RSV, however, remains limited, controversial, and mostly supportive.