The efficiency of embryonated eggs and primary monkey kidney cell culture for isolation of contemporary influenza viruses was compared over three seasons by parallel inoculation of clinical materials. For the type A (HlNl) strains of 1977-1978 and for type B strains eggs were very inefficient, and nearly all viruses were isolated in cell culture alone. For the type A (HlN1) strains of 1978-1979 and for type A (H3N2) strains, isolations were more frequently made in eggs, but even here eggs were

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... ot as efficient for primary isolation as were cell cultures. It is concluded that primary monkey kidney cell cultures can be used as the single system for primary isolation of current type A and B influenza viruses.