Biological properties of influenza viruses A (H1N1), that were the cause of the infection in humans in April - May 2009, and the action of the Russian antivirals on their reproduction were studied in vitro. The nucleotide sequence in the viruses was determined and followed by detection of the mutations responsible for resistance to the antiinfluenza drugs. The experiments showned that arbidol and ribavirin had a selective inhibitory action on reproduction of the viruses in the MDCK cell culture while rimantadine had no affect on their reproduction. The data were confirmed by the results of the genome analysis in influenza viruses A/California/04/2009(H1N1), A/California/07/2009(H1N1) and A/Moscow/01/2009(H1N1)swl, that revealed no replacements defining the resistance to arbidol while the viruses contained a mutation in position 31 of M2 protein, responsible for the resistance to adamantans.