Sixty products, derived from marine organisms, typical of the Bulgarian Bla
ck Sea coast, were examined for inhibitory activity on the reproduction of
influenza viruses in tissue cultures. The antiviral effect was investigated
by the reduction of virus infectivity. Using representative strains of inf
luenza virus it was shown that apparently the-inhibitory effect was strain-
specific. The most effective products were further studied in fertile hen's
eggs and in experimental influenza infection in white mice.