During the last ten years most communities in the United States have experienced at least 11 outbreaks of influenza virus infections. Beginning with the last influenza A virus epidemic of the H2N2 (designates the major surface antigens of influenza A viruses, H for hemagglutinin and N for neuraminidase) (Asian) era in the winter of 1967-1968, we have been assaulted during almost every respiratory disease season with either influenza A or B viruses and on one or two occasions, depending on location, both viruses. Viruses of the influenza A/Hong Kong family (H3N2) first appeared in late 1968 and have produced epidemics with excess mortality on six occasions through the winter of 1976. Influenza B viruses have caused outbreaks in most localities during four different years, including the current one (1977). All of these epidemics produced notable morbidity in the pediatric age group and resulted in hospitalization of many children.