Despite the plethora of antibiotics available for the treatment of bacterial infections, very few agents have been developed to treat viral diseases. Ribavirin (Virazole) is a triazole nucleoside antiviral agent that produces selective antiviral effects against a broad spectrum of RNA and DNA viruses. The drug has been effective in the treatment of naturally occurring influenza A and B infections when administered by aerosol; oral administration has been ineffective. Ribavirin aerosol therapy also has proven effective to reduce symptoms of respiratory syncytial virus infections in young adults and hospitalized neonates. Ribavirin aerosol may be the first antiviral agent to treat these common diseases.