The appearance of a swine type of influenza A among recruits in Fort Dix, New Jersey, in 1976 prompted an evaluation of the sensitivity of this virus to amantadine - HCl. Well-tolerated levels of the drug effectively blocked replication of the influenza A/New Jersey/8/76 (Hsw1N1) virus isolate in three laboratory models: monkey kidney cells, embryonated eggs, and intranasally infected mice. On a comparative basis this virus would appear to be more sensitive to amantadine - HCl than human influenza A strains, including the recent Victoria (1975) strain. All strains of influenza A virus continue to be sensitive to amantadine - HCl.