A study of two inactivated monovalent and polyvalent influenza vaccines in the winter of 1965 among secondary school pupils in Anchorage, Alaska, is reported. Two successive waves of infection with influenza virus A2 and B occurred which were closely related antigenically to the vaccine strains A2/ Taiwan/1/64 and B/Maryland/1/59. Protection in the vaccinated group was evident, as expected, and the order of efficacy of the vaccines was around 50 to 60%.