Respiratory viral infections are implicated in both the pathogenesis and exacerbation of asthma. Infections with respiratory syncytial virus and parainfluenza virus are the major cause of wheezing-related respiratory infections early in life. Infections in early childhood affect the immune system and modify the risk for subsequent development of allergies and asthma. Later in life, rhinovirus and influenza are implicated frequently in the exacerbation of asthma. The management of respiratory viral infections includes adequate prophylaxis and treatment of acute infections. Insights into the mechanism of viral respiratory tract infections will provide therapeutic targets for treatment and possibly the prevention of virus-induced asthma.