After the isolation of A/New Jersey/76 (Hsw1N1) influenza virus from five soldiers at Fort Dix, New Jersey, case finding was initiated by obtaining specimens for viral isolation from 95 patients with acute respiratory disease and determining antibody to influenza A/Mayo Clinic/103/74 (Hsw1N1) antigen in paired sera from 74 soldiers who had been hospitalized with acute respiratory disease. Influenza A/New Jersey virus was not isolated, but serologic studies identified eight additional soldiers as A/New Jersey influenza patients. Development of heterotypic antibody to A/Mayo Clinic antigen following infection and/or immunization with influenza A (H3N2) strains was studied and was found to occur infrequently. One of the 13 identified patients had died, and postmortem findings were consistent with viral pneumonia. Four of the 12 surviving patients had radiologic evidence of pneumonia, but clinical syndromes in all 12 were similar to those described for other influenza A infections.