In an outbreak of influenza virus A/England/333/80(H1N1) infections in college students, 14 randomly selected patients were treated by inhalation of ribavirin small-particle aerosol through a face mask. They retained an average estimated 1.15 g of drug in 23 h of treatment given over 3 days. 17 patients served as controls. Ribavirin aerosol treatment had a therapeutic effect judged by the highly significant reduction in height and duration of fever, reduction in systemic illness, and disappearance of influenza virus from respiratory secretions. 1 additional patient with influenzal pneumonia caused by a strain of influenza virus A/Bangkok/79(H3N2) recovered promptly with ribavirin aerosol treatment.