Amantadine hydrochloride, a stable, white crystalline amine of unusual symmetrical structure, is a new antiviral agent that may be useful for the prevention of illness caused by various influenza A2 (Asian) virus strains in man. Although observations have not been made in epidemics, the results of controlled studies in experimentally infected human volunteers have shown its partial efficacy (50%) as a prophylactic agent for several strains of influenza A2 virus. The drug is of no value as a therapeutic agent and should not be given after clinical signs of infection appear. In times of a demonstrated influenza A2 epidemic, amantadine may be used concomitantly with vaccine as a prophylactic agent. The drug is indicated specifically in patients of all ages for whom influenza A2 infection would entail a grave risk, and it is indicated particularly in these patients when vaccine cannot be used. A dosage schedule for infants under 1