Table III summarizes clinical applications of antiviral agents in respiratory viral infections. (table: see text) For influenza A virus infections, both oral amantadine and rimantadine are effective when used for seasonal prophylaxis and for prophylaxis in institutional populations. Both of these drugs, as well as aerosolized ribavirin, have antiviral and therapeutic effects in uncomplicated influenza. It remains to be determined whether any of these modalities or possibly their combined use [44] will be useful in treating severe influenza hospitalized patients or whether they can prevent the development of complications in high risk patients. Unfortunately, there is no parenteral formulation of amantadine or rimantadine for use in critically ill patients. Aerosolized ribavirin has also been shown to have modest therapeutic effects in influenza B virus infection. However, a major need exists for an antiviral which is active against influenza B virus and which can be used on an outpatient basis. Controlled clinical trials have shown that aerosolized ribavirin therapy improves arterial oxygenation and modifies the severity of respiratory syncytial virus bronchiolitis and pneumonia [3,5]. Its role in treating life-threatening disease or in modifying the long-term sequelae of RSV infections are unknown at the present time. Again, a specific antiviral agent is needed for outpatient use in preventing or treating RSV infections. Finally, after over a decade of work since the original observation that intranasal interferon could prevent experimental rhinovirus infection [11], recent studies have established that intranasal rIFN-a2 is effective in the postexposure prophylaxis of rhinovirus colds in families [42]. This strategy needs to be studied with regard to the prevention of infection and its complications in high risk patients and it remains to be determined whether intranasal interferon will have therapeutic activity in established colds.